12 August 2026 84% partial solar eclipse.

 ~*~

  Wednesday 12th The partial eclipse lasted from 7-9pm. With maximum obscuration of 84% at 20.04 CET. 

 I knew well in advance that it was going to be difficult to see past the local obstructions. There are huge garden trees, a windbreak wood and assorted trees in the paddock to the south and west of my rural home. Local solar altitude would be 6º to the WNW. 

 By sheer chance it had been mostly sunny all day but with plates of cloud crossing at intervals. I was hoping to take a few snaps with my mobile phone camera. Tracking the sun would have required a 100m long mains, extension lead snaking along the gravel drive to the south. 

 I had no such extension lead and no desire to spend so much money on three x 40m leads! Even if I had the power. I was in no position to carry my heavy Celestron Advanced stainless steel tripod very far. Nor its AM5N mounting. I get breathless just walking the near 100m length of the drive to the junction! Having reached 79 with clogging of the heart arteries. Despite the hundreds of thousands of miles of cycling and the excellent care of the hospital heart departments. Four stents and a balloon expansion so far. I take eight tablets every morning to keep my blood pressure low.

 So I really needed a mobile, lightweight set-up. I dismantled my modified Lunt 60 to the 102mm TechnoSky APO, H-alpha telescope. I refitted the 2.5" Feather Touch focuser and found my longest photographic dovetail plate. 

 The Manfrotto carbon fiber tripod would be fitted with a photographic gimbal mounting. Making a set-up I could carry in stages along the drive. To use the access gates as peepholes in the neighbour's overgrown, 2m high, Spirea hedge. That's me perched at the first gap in the hedge. Captured by one of my security cameras. Which are great fun in themselves. 

 The 1.25" Lunt Herschel Wedge would be my safety device for solar observing. I elected to fit the TS binoviewer with 26mm Meade 4000 26mm eyepieces. Though I needed the lowest power TS GPC to reach focus.

  A 1.25" Solar Continuum filter provided the garish apple green filtration. Which is a handicap for colour photography but makes viewing so much more comfortable and sharper. Though it is not intended as a solar safety device. I was immediately able to see 6 small groups of spots. Without the filter I struggled to focus. Even on the largest pair of sun spots near the limb. Suddenly the umbra and penumbra snapped into sharp focus. 

More to follow: 

 

 

  ~*~

 

3rd July 2026 Etalon spacing.

 ~*~

 Friday 3rd I set up the 102mm APO with 60MT etalon in the drive. It was blowing a gale from the NW. So this was the only real shelter where the sun was still visible. In between huge clouds.

 I am using the mini-PC indoors. So it was not readily available for astronomical duties and imaging. I had to make do with visual observation only. All I really wanted was confirmation of surface texture in H-alpha. I made a slight alteration of the spacing to about 18mm of the Omegon extension still visible. 

 The ZWOAM5N mounting is sitting on top of a PE200 pier extension. All mounted upon a Celestron Advanced tripod with 2" stainless steel legs. 

 

The tail end of the H-alpha set up. With the Lunt LS60MT etalon, housing and focuser. 

 I am using a 2x Shorty Barlow. To reach focus with a TS star diagonal and the Magnum 8-24x zoom eyepiece.  A solar wedge [diagonal] is not needed with an H-alpha set-up.

 

 

 

 

 

 

Close-up of  the tail end of the 102mm where the focuser would normally fit. Showing the bored out 2" x 35mm Omegon extension and the Lunt 60MT nose clamped in plumbing fittings.

 Ideally I need to introduce a threaded fitting to allow fine adjustment of the etalon spacing from the objective. Some sort of push-pull arrangement if possible.

 My ZWO174mm camera needs to be fitted in place of the star diagonal and eyepiece. So that I can use imaging software to confirm the best possible spacing between the telescope and the etalon. A much less cloudy day would reduce the considerable frustration of waiting for clouds to clear the sun.

 

 

  

  ~*~

 

1st July 2026 Summary of the modified 102mm H-alpha telescope.

 ~*~

 Wednesday 1st. Mostly overcast. I had to wait at home for a delivery. So used the intervening time to rebuild the 102mm TecnoSky APO refractor as a modified H-alpha telescope. Much of the detail here is a duplication of a number of earlier posts. Posted as I developed my ideas for modification. I have summarized the details here so they are hopefully much easier to follow in one place.

 After my last viewing of the sun in white light. I had left the Lunt 60MT etalon module and focuser unattached. The Feather Touch 2.5" focuser had proved to be ideal for white light and had the same thread size as the TecnoSky focuser. 

 I still wanted a more stable connection between the two major components. The Lunt 60MT etalon module and the TecnoSky 102mm APO telescope. Which involves removing the focuser from the APO telescope. To allow the Lunt etalon module to be attached more closely at the rear. The Feather Touch adapter ring is left in place. The TecnoSky focuser's base ring/rotation adapter is not as useful as the Feather Touch. Though it could be adapted if desired. The base ring is also deeper than the FT adapter. This might not matter. Provided there is still room for the Lunt 60MT etalon at the correct spacing.

 The etalon's nosepiece must be placed 264mm inside the APO's focal plane. The focal plane is 735mm from the front edge of the fully retracted dewshield. The focal length is quoted at 714mm. The APO's main tube is 460mm from the retracted dewshield tip. To the edge of the Feather Touch focuser rotation/adapter ring. So the Lunt etalon's nosepiece should be 11mm beyond the adapter ring.

 Or not? The focal plane is where it is relative to the dewshield. Regardless of any adjustments to this measurement for the exact position of the objective lens. So 735 - 264 = 471mm from the front edge of the retracted dewshield. This is where the nose of the etalon should lie. About 20mm more than the present position. Unfortunately I shall have to wait until tomorrow afternoon's promised sunshine to prove it. 

 The image [top right] shows my original assembly. With the etalon nose extension inserted and centered. By a marine plywood ring in the empty, FT focuser, rotation ring. The extension is a standard, short, 35mm, bored out 2" fitting from Omegon. The nose of the Lunt etalon is rather oversized for a 2" standard push fit extension. So I bored out this extension in my old lathe.  To increase the internal diameter to 52mm. Only to a depth of 25mm in the female half of the extension. I also had to increase the depth of the groove which houses the bronze clamping ring. Which was much more fiddly. 

 I really wanted to fit a permanent spacer. To ensure the two components would always be close to the desired spacing. Unfortunately there isn't room for a focuser in the gap between them. Which would have been preferable. To allow fine adjustment and more accurate centering. With a positive clamp on the 2" etalon nose piece once the best position was found. 

 It would take a brave and skilled man to shorten the APO's main tube and re-thread it to match the original. The old fashioned way of using radial fixing screws has been replaced by precision, CNC machining.

 My final solution will be to turn a thick, aluminium ring. To replace the temporary plywood ring with something more solid. Probably with a turned V-groove. To match the Feather Touch adapter and its nylon pointed rotation and clamping screws. Most Feather Touch focusers have this V-groove turned in the bases. To allow secure and silky smooth rotation of the entire focuser. With no sloppiness or loss of concentricity.

 Before that happens I must absolutely confirm the required spacing. The quality of the H-alpha image depends entirely on this dimension being correct. Not just to tune closely to the H-alpha wavelength but to obtain even lighting and detail across the entire sun's disk. Or camera's field of view. 

  

  ~*~

24.04.2026 White light solar observing.

 ~*~

  Desite having hurt my back a week ago I dragged the new rig outside. Hoping to do some solar observing in white light. I did not connect the mini-PC. Just used the paddle.

 First I tried the Lunt 1.25" solar wedge. Then I fitted the Lacerta 2". Which provides dimming by rotation of the EP holder. I started with a single Meade 4000 26mm EP. Then my 2x Shorty Barlow, Zoom EP and finally TE binoviewers and a pair of 26mm EPs. 

 The latter was by far the most satisfying set-up. The sky was milky but there was no visible cloud crossing the sun. The seeing was mostly very soft  but with moments of tantalizing, razor sharpness. Most of the time I was focusing in and out. Just trying to get a sharper image. When there was often, literally none to be found. I did not bother to use my mobile phone to capture the fuzzy image. Nor bring out the ZWO 174MM. Which would have required a screen and mouse mat.

 Earlier plans to have a permanent pier in front of the greenhouse were never progressed. The endless cloud and cold wind did not give way to sunshine until this last week. I only had an hour free this morning before leaving for a heart scan at the city hospital. I still have plans to put one of my piers in the front garden. Unfortunately I hurt my back playing with heavy paving slabs a week ago. So I can't possibly manage moving the massive weight of any of my three piers. Each of which needs different adaptation to the ZWO AM5N base.

  ~*~

1st April 2026 MkIV packing and parcel delivery delay.

 ~*~

 UPDATE: 22nd April: Two of the parcels reached the recipient. The third, in the foreground of the image below has only just arrived after three weeks. Damaged at both ends but the contents remained intact. Largely thanks to my taping the axis shafts to the MkIV's huge, saddle casting. I also fixed the locking collars to the ends of the shafts. Even so both ends of the parcel were punctured.

 Wednesday 1st April. Sunny. I have been outside packing the MkIV for its trip back to Blighty.

Having taken the whole thing apart. So I was able to tape the main shafts and cradle together. Then place it in a long, narrow box with padding. I was hoping to avoid the heavy shafts shooting out of the box and causing damage. Taping the parts together also increases the cross sectional area. I also taped the box thoroughly. To avoid penetration. This parcel came to 14kg. So just under the 15kg postage step.

 The rest of MkIV just fits into an old banana box. However it came to just over 21kg once I had added lightweight packing materials.

 The weight limit is 20kg for handing packages into parcel centres in Denmark. So I will have to lighten the second parcel and make up a small third.

 16.30 I have just delivered the three parcels to the parcel office in the village. 2 x15kg and one of 10kg. 

 

  ~*~

23.03.2026 MkIV dismantling.

 ~*~

    Monday 23rd. Bright but cloudy. Rather cool. I have continued to struggle with the removal of the main shafts of the MkIV. I had fitted stainless steel shafts in place of the rusty originals. This was years ago. I had fitted clamping screws to ensure th safts didn't detach accidentally. The fit must have been close. Because the shafts didn't want out come out of the castings. 

 11.30 In the end I used a compact counterweight as a slide hammer. With two shaft clamps well tightened onto the end of the shafts. The castings were resting on 2x4s on a folding workbench. This has taken me a couple of hours but the shafts are finally free. I can now pack the MkIV into compact boxes. Or wrap the parts. Rather than have to cater for huge L-shapes. The Dec shaft is by far the longest and the saddle is quite a length. 

 I have started to weigh the components but decided I need a rest first. 

 Lunch over. I have weighed all the MkIV's components. The total comes to 28kg. There are parcel services which allow 30kg. Or I could split the load two ways.

 

 

 

 

 

  ~*~

20.03.2026 Downsizing Pt.2. The MkIV is going.

  ~*~

 Finally a reasonable day to be comfortable working outside. Warm sunshine [46F/8C] and no wind. Though there was a light overnight frost and thick mist. 

I have been using a tall, tripod ladder, chain hoist and slings to lower my old Fullerscopes MkIV telescope mounting down from its massive steel pier.  The pier was so embedded in the undergrowth that I needed the car and a long rope to pull it free! 

 I welded the pier together and placed the restored mounting on top while I was still at work. So at least 18 years ago since my retirement. I must have been much stronger, inventive and determined back then. I stripped and painted the mounting. Fitted stainless steel shafts and silvered the scales. 

 The mounting was used to capture the Mercury Transit with my 7" [180mm] F12 refractor on board. Which lasted so long that it fried a big transistor in the speed control electronics for the synchronous drive motors. 

 Now I am dripping with sweat and a bit tired from the effort required today. I still have to dismantle the mounting and pack it up for postage to its new owner. That should be fun! Everything is rusted. 

 

 ~*~ 

24*12*2025 Downsizing!

 ~*~

  Tuesday 24th. I have listed my larger telescopes and accessories for sale on Solarchat! The specialist solar astronomy forum on the WWW. 

 I shall never use these items again due to their bulk and weight. Making handling without a permanent observatory beyond my advancing years. 

 Though English, I am now based in central Denmark. So anybody outside the EU will probably face import taxes and hefty freight charges. For which global buyers will be responsible. 

https://solarchatforum.com/viewtopic.php?t=51690 

In the hope of reaching a larger audience for these unusual items I have now listed them on Stargazerers Lounge. European Section small ads. 

 https://stargazerslounge.com/topic/441127-aging-amateur-astronomer-downsizing/

 

 

  ~*~

1st December 2025 Patience!

 ~*~

  Monday 1st. For the second day in a row the sun is teasing through thick cloud. No sunshine is forecast but there it is. Brief brightness through blue holes. I managed to capture a few videos yesterday. Though really, none worth sharing. The image is probably upside down. 

 11.00 It is still too early. For the sun to shine usefully through the small dormer window. Where I have the telescope set up on the upstairs landing. Aimed through the window for when, or rather if, it shows itself again. For long enough to be worth capturing. 

 The sky is quite blue to the north and dense to the south. I shall just have to be patient. I am glad to be indoors today. Rather than sitting in my cold observatory. Waiting endlessly for the sun to clear. While the wind whirls around me.

 I still have to confirm the best position for the Lunt etalon inside focus. Having re-attached the bored out, 2" extension to the nose of the etalon. It's exact position still needs to be fixed. For the most even H-alpha detail across the entire solar disk.  

 The sun never reappeared. 

  ~*~

21.11.2025 Removing the blinkers.

 ~*~

  Friday and the sun is out while I am at home. I was waiting for the sun to align with the small, dormer window. So that I do some more imaging from the comfort of being indoors. Patience is certainly required. 

 This image was captured this morning through the double glazed window. I adjusted the etalon:focus distance to produce the most even surface detail. Perhaps a little brighter at center of the disk.

 When I peered out of the window. To check where the sun was shining. I noticed something new. Everything on the east side of the house is in deep shadow. From the absent neighbour's trees. Nothing new there. Then I noticed the patch of ground on the western side of the greenhouse. This was enjoying almost uninterrupted sunshine. 

 This had never been possible in the past due to the tall front hedge. Now reduced to head height. Several foolishly tall conifers have all been removed. Leaving only a couple of shrubs. Which I had reduced to a couple of meters in height. These could well be lowered further. A bit of trimming of some shrubs to the west would give me plenty of room to set up the solar telescope. While still providing shelter from the prevailing SW winds. I'd get hours of uninterrupted sunshine.

 It's not the easiest place to reach at the moment. Because of legacy hedges and shrubs. Which I was never allowed to touch. Now I am in sole charge of the garden I can choose to hack back what I like. This space was previously closed to my mind. By all the years of adjusting to foolish overgrowth. 

This area lies outside one kitchen window. Just beyond the kitchen sink. There is no reason why I couldn't set up the monitor and keyboard in the corner of the kitchen. To control the AM5N mount and ASI174mm camera. I would still enjoy the comfort of being indoors. While the telescope would be looking over a paddock and then endless fields beyond. With few thermal issues to worry about. 

  ~*~

17.11.2025 Imaging through a window.

 ~*~

  Monday 17th It was after 12.00 before the sun reached the telescope through the small, double glazed, dormer window. Opening the window produced fierce, thermal agitation of the image.

 
 Here I have added the Lunt 60MT etalon to the 102mm Apo. Not bad for a first attempt. The optics weren't well aligned. The sun had moved too far to the west to allow a clear shot. At least I have a reference for etalon to focus spacing now.

 

 

 

 

 

  ~*~

15.11.2025 White light imaging [badly.]

 ~*~

  Saturday 15th. Finally sunshine.

 I am set up on the upstairs landing. 102mm F7 Tecnosky Apo, assorted filters, Lunt 1.25" wedge, ZWO ASI174mm camera. AM5N mount, AVX tripod. 
 

Pointing at the sun through a double glazed, dormer window. Opening the window resulted in violent thermal agitation of the image.

 

 

 

 

 

  ~*~

13.11.2025 Indoor solar imaging?

 ~*~

  Thursday 13th Another grey, cold and windy day is forecast.

 I have made no progress on the modified H-alpha solar telescope. On the rare occasions the sun was out. Then so was I.  

 A flash of sunshine this morning had me wandering outside looking for clear views. The combination of low sun and all the trees made it impossible until much later. Even then it would be no fun with the wind gusting to 15m/s or over 30mph. Temperatures will peak at 12C/54F at the most this afternoon.

 I checked upstairs. There was no chance of setting up a telescope to peer through any of the windows. At least, not until much later. When the sun had moved further to the south. Which meant I could place the tripod on the upstairs landing in anticipation. To see the low sun through the small, south facing, dormer window. I could easily compare the view through the glass. Or with the window open. 

 Of course it quickly clouded over again. Still well worth setting everything up I think. I could practice my solar imaging in white light. In some comfort and with everything easily to hand. No traipsing back and forth with forgotten items. To the far side of the parking area. Just to see the sun fleetingly over the absent neighbour's trees. 

 The telescope can be set up and simply left in place. There are months of cold weather ahead. Why not give it a try? I can add the H-alpha components as and when it would be worthwhile. Hopefully with long hours of sunshine to make the adjustments more relaxing. 

 The afternoon sky was leaden. I had everything set up on the landing. So I captured an ash tree at 100m rocking in the wind. Showing some very fine detail despite the heavy overcast. Then I stacked the video for a bit of practice with the software.

 Before closing down I remembered to return the telescope to its parking position. Pointing at the N-pole. Had I left it looking out of the window. The sun could have come out and caused overheating or even a fire. The AM5N mount likes to be sent Home at the end of each session. Before switch off. Press the lower button on the paddle for a few seconds. Then wait for all movement of the mounting and telescope to finish. 

 Here is my blog post from 2019 showing the use of SharpCap Pro to align the mounting on the sun:

 Fullerscopes Telescope Mountings: Whoopee! Polar alignment using SharpCap and the Sun!

 Direct link to the YT video: 

 https://youtu.be/zRT-HsRsftI?si=PXf6JDm0mVVcCONK

 A later YouTube guide to drift [Polar] alignment on the sun.  Note the use of coloured reticules/reticles for fine adjustment. This is an additional step not show in the first video. 

 https://youtu.be/pw_xfPW4nYQ?si=Kh74Q_xi0CjsKAne

NOTE: You will need an astro camera attached to the telescope with approved solar filtration. 

  ~*~

27.10.2025 102mm APO and Lunt 60MT etalon spacing.

 ~*~

 Monday 27th. Sunny for most of the morning. Then clouded over in time for lunch. The forecast was a sunny afternoon.

 I dragged the tripod, mounting and 102mm APO refractor outside. There followed some hours of experimenting with etalon distance from focus. I was able to focus the red sun but couldn't see any H-alpha detail in the image. There was one major spot and two smaller ones.

 After lots of trial and error I rechecked where the focus lay relative to the refractor's focuser mounting ring. Only to discover I had been using the wrong measurement. The 60MT etalon was about 41mm too far in towards the objective. I needed the etalon nose to be 264mm from focus. I made some more adjustments and finally saw some filaments. 

 13.30 Lunch over and the sun seems to have come out again. I shall go back out and do some more testing.

 There was only a little sunshine after lunch. I double checked the focus relative to the focuser adapter ring. 290mm. The clouds actually helped to identify sharpest focus. 290-264=26mm. So the original position of the etalon wasn't too far out. Though that doesn't explain the lack of H-alpha detail. 

 Coarse changes in etalon spacing are possible. By moving the pipe clamps in the dovetail slots. While fine or coarse changes are easily achieved. Simply by loosening the main tube in its rings. Then sliding the main tube and its objective through the rings. Gentle rotation helps here.

 I spotted several proms on the limb after lunch. A double hump and a triangular sail. The latter looked as if it was about to detach. 

 Screwing in the pressure tuning knob made the proms disappear as expected. So the tuning is working and the instrument must be showing some H-alpha. Otherwise these proms would not have been visible at all. Though strangely, I was no longer able to see the filaments. Nor any H-alpha, surface texture. 

 Increasing cloud and wind made it pointless to continue. Tomorrow looks like rain!

 

  ~*~

26.10.2025 PT. 2 102mm H-alpha APO Lunt 60MT etalon.

 ~*~

 Sunday 26th. Wet and windy with fleeting sunshine after 15.00. Sadly it is far too cloudy to be worth trying the telescope on the sun. With only a few second visibility in the last hour.

 I shall share some images of my Lunt 60MT H-alpha conversion of the 102mm Tecnosky APO refractor. It is all mounted on a PrimaLuce 50cm long [Losmandy style] dovetail plate. The APO uses its original tube rings. Though only the single, M6 central screw holes can be used. The spacing of the holes does not match between these rings and the dovetail plate. 

 The obscenely high price of PrimaLuce tube rings. Prevents me from buying a pair. Just to ensure the correct spacing. To allow pairs of screws to be used for attachment. A spacer block adapter with suitably spaced holes. Would allow two screws, per ring, to be used for extra security. I'll see if I have the patience to make a pair of adapter blocks from aluminium.

 The bosses of the tube clamps can be seen bolted directly to the dovetail plate. As mentioned in previous posts: I needed to buy 6 to 10mm thread inserts. To adapt the 6mm screws for the dovetail plate. To match the 10mm pipe clamp threads. Note the thick rubber gaskets. Which nicely protect the high quality finish on the Lunt telescope parts. 

 The plywood ring was turned on my lathe. To centre the Lunt 60MT etalon on the OTA focuser ring. Except, of course, I have removed the complete focuser from the Tecnosky OTA. The focuser ring shown is from a 2.5" Feathertouch focuser. 

 I sent the Tecnosky focuser back to Telescope-Service for "adjustment." It was far too rough to be used as supplied. [Brand new!] They promised me a few days turnaround. It has been three weeks. 

 Fortunately I am in no hurry. I am not using a focuser in this H-alpha modified refractor. It was sheer luck that the FT ring also fitted the APO tube thread of M91. The main focuser had to be removed anyway. To allow the etalon to function correctly at 461mm inside focus of the APO. Which has a stated focal length of 714mm. [102mm x 7.]

 I have retained the Lunt 60MT R&P focuser behind the etalon housing. The knurled thumbscrews are an addition. To replace the pointed grub screws supplied by Lunt. More pointed thumbscrews would have been better. 

 The focuser houses the Lunt BF1200S blocking filter. Which has a nominal 2" body. Most solar telescopes employ a blocking filter based on a star diagonal. I chose a straight through model when purchasing it alone. To obtain a larger clear aperture. The tail end of the adapters has a T2 thread and 1.25" clamping ring to hold en eyepiece or my ZWO ASI174MM mono astro camera.

 

  ~*~

 

 

 

 

 

26.10.2025 Down with the bosses!

 ~*~

 

 Sunday 26th Another wet and windy day in series. 

 I have not made much progress on the pipe clamp mods. For holding the Lunt etalon onto the extended dovetail plate. Which in turn is holding the 102mm APO without its focuser.

 Clamp bosses with threaded 10-6mm inserts/reducing adapters.

 The bosses are slightly too tall at 20mm. Relative to the OTA in its tube clamps. Made far worse by the threaded inserts. Which convert the bosses to a useful M6. Anything larger in diameter. Would mean modifying the dovetail plate by drilling. 

 Having tightened the threaded inserts fully. I must now saw them off flush with the bosses. This would still demand that the 102mm OTA's tube rings must be packed up sightly. To ensure the etalon is concentric with the OTA. I would rather not shorten the bosses. To avoid shortening the threaded inserts any further. Though I may be worrying unnecessarily.

Bosses reduced to 18mm tall. The reducer inserts are brass. With plenty of thread left. I used an angle grinder to make quick work of it. Followed up with an orbital sander to smooth the bosses.

 I had intended to bolt 18mm plywood to the dovetail plate. To sit under the etalon. With two, 15mm Ø holes at 22mm centers. Drilled in the plywood for the clamp bosses.

 When I should really be using 20mm ply. To bring the bosses to the height of the dovetail plate. While using 18mm ply and filing the bosses down to 18mm. Which should bring the etalon to OTA level. Too much text and not enough sawing! 

 I assembled the H-alpha telescope without the plywood as seen here. The dewshield is fully retracted. I still need to confirm etalon position and the resulting camera focus. Which will require some sunshine. We are going through a long run of changeable weather. Mostly gales and rain. 

  ~*~

8.10.2025 Etalon adapter ring.

 ~*~

  I needed to be able to use M6 machine screws. To hold the pipe clamps to the dovetail bar. Without having to make oversized holes and enlarged slots. The clamps were threaded both 8 & 10mm in the bosses. So I bought some threaded adapter bushes. 6-10mm. 

 They are rather long to fit deep enough into the clamp bosses. I have yet to see how high the bosses will stand off from the dovetail plate. Once the etalon nosepiece is centered in the FT rotation ring. If the spacing is enough then I need not modify the threaded bushes. If too short a spacing. Then I must saw off the excess protrusion of the bushes. 

 If I am lucky I can use a plate of some sort. To maintain the clamps distance from the dovetail plate. With the bosses passing though suitably sized holes. The bosses can then be pulled down tight onto the dovetail plate. Rather than onto the protruding threaded bushes. The measurement to the centre of the ring and to the centre of the nosepiece. Is really quite close to each other at 60mm. 

 15.30 I have turned a marine plywood ring. This fits snugly in the FT rotation ring. The plywood ring is being secured by the FT rotation ring's pointed screws. While holding the etalon nosepiece centralised. The pipe clamps' bosses are actually close to the correct height. Unfortunately, the threaded bushes project much too far. 

 So, should I saw off the projecting threaded adapters? It makes the most sense. I then make a plate, probably in plywood first, to ensure accuracy. To support the pipe clamps and to fix the lateral location of the projecting bosses underneath. This plate would be bolted to the long dovetail bar. With the provision to allow the Lunt etalon to slide along the axis during fine tuning. 

 I can make an aluminium plate afterwards. Once the exact location of the etalon, relative to the APO telescope's focus, is confirmed. There is considerable weight involved in the Lunt etalon housing and the following focuser and camera supports. This must all be held firmly and safely on axis. Without sag or twisting under its own weight.

 

  ~*~

3-8.10.2025 APO focal plane and Lunt 60MT H-a etalon positioning.

 ~*~

  After lunch I set up the bare Tecnosky OTA on the long [Losmandy] Prima Luce dovetail bar. Then mounted the telescope on the ZWO AM5N on the AVX tripod. With the telescope tracking the sun I was able to make repeated measurements to the sun's sharpest image as accurately as possible.

 I wanted to know the distance from the focal plane to some fixed reference point on the telescope. I chose the tip of the retracted dewshield as my reference point. 

 Mock-up of the position of the Lunt etalon. Relative to the 102mm APO telescope. Primary focuser removed.

 After repeated measurements I decided the sun's image was sharpest at 735mm. With the focal length stated as 714mm this placed the objective 21mm behind the forward edge of the retracted dewshield. 

 The rear of the Feather Touch focuser's rotation ring is 460mm from the front of the retracted dewshield. This second reference point would be 439mm from the objective. 460 - 21mm. It was this ring which would support the tubular adapter I intended to turn on the lathe. 

 The FT focuser body would be removed entirely. Leaving the distance to the Lunt etalon to be determined by the 264mm from focus rule. To match Lunt's own measurements in the 60MT. The Lunt etalon will also be supported on three, radial, pointed screws in a circumferential, dovetail groove. Just like the FT focuser.

 714 - 439 = 275mm. So the etalon must be supported at 275 - 264mm = 11mm behind the FT rotation ring. The tubular adapter will be approximately 85mm long. To reach to the front face of the Lunt etalon housing.     

 If I can find, or make, a supporting ring for the 76mm Ø, Lunt etalon housing. Then this would allow fine tuning of the etalon position relative to the focal plane. The exact, linear position of the etalon, relative to the focal plane, is important for the best possible H-alpha image. It is this position which sends parallel light through the etalon. Which also needs to be concentric of course.  

A simple, rubber lined, pipe clamp [or two] can be used to hold the Lunt etalon for tuning trials. The etalon will be attached to the Lunt focuser. Making for a rather weighty assembly. So stiffness in support is vital. A pair of clamps in tandem can be bolted to the dovetail bar. Which has useful slots for linear adjustment.

 If the pipe clamps are successful. Then a simple, bored disk of marine plywood can be clamped in the FT rotation adapter. Using the pointed dovetail screws for clamping. This will provide perfect concentricity and support. For the 52mm nosepiece of the etalon. While simultaneously allowing for sliding, linear adjustment. 

 Here is an image of the two 76mm pipe clamps in place. Attached to the Lunt etalon housing. They are quite smart and don't look too out of place in this context. 

 These clamps are usually fixed to the supporting wall with M10/M8 bolts. Which is much larger than the M6 standard of the dovetail bar. I may saw off the attachment bosses. To allow an M6 countersunk head screw. To allow an M6 fixing through a spacer. 

 Or, the rubber sleeve can be lifted. To allow M6 CSK screws to pass right through the bosses from the inside of the clamping ring. This will leave the bosses to provide very firm support. Without any loose parts. 

 A smaller clamp on the 44mm Ø camera extension. Could provide further support at the tail end. There is no room on the Lunt, R&P, compact, focuser body for clamps. The camera's exact position is still an unknown. Which is where the Lunt focuser comes into play. With assorted 2" and T2 extensions available.

  I think I am finally getting there. With a safe and working trial assembly for H-alpha etalon, linear tuning. I like the fact that no precise machining or expensive accessories are needed.   

  

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1st October 2025 Sun photos with phone

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  After hours of waiting for the clouds to clear I captured some phone "snaps" of the sun. T-S binoviewer, 26mm Meade Plossl, GPC, Lunt 1.25" Solar Wedge, Bresser phone clamp. I was using slight digital zoom on the phone's camera to better fill the field of view of the screen.

 It would have been better to have used a single eyepiece. The binoviewer has optical limitations and adds a lot of glass to the light path. Which must be addressed with a GPC. Glass Path Corrector. 

However, the binoviewer adds a great deal of  enjoyment to the visual view. It gives a real sense of floating above the solar surface. The detail seems to be greatly improved in comparison with a single eyepiece. In fact I struggled to see as much detail with only my dominant right eye. It seemed as if it was going repeatedly out of focus. Perhaps a symptom of my age. I struggled to see the numerous pores. Which were easily visible when using both eyes.

 I have yet to enjoy binoviewing in H-alpha with the new telescope. This is a tricky subject and requires strict adherence. To the optical spacing of the elements involved. My choice of an f/7 refractor was deliberate. To match the original Lunt 60MT. 

 The problem is getting the Lunt etalon far enough inside focus. Which would require the complete removal of the focuser. Not easily achieved but not impossible. I shall have to resort to my vintage metal lathe. To make an aluminium adapter ring. The rest of the optical chain will be hanging from this ring. So it needs to be accurate. 

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30.09.2025 Tecnosky 102mm APO to Feather Touch focuser swap.

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  Tuesday 30th. I was pleased with my new telescope optically. Though NOT the R&P focuser. Hours of fine adjustment would not allow smooth movement. If it was smooth, then the slow motion stopped working. Finding a balance was a nightmare! I emailed the dealer and they responded with a focuser instructions leaflet. It was useful guidance but didn't help me achieve smoother motion.

 By the strangest coincidence I had a Feather Touch 2.5" focuser on my 6" H-alpha 'scope. The one I wasn't going to be using again. Because it was too big and too heavy. Could the FT focuser be made to fit the Tecnosky? 

 It all hinged on the size of the rotation ring/focuser adapter. I donned clean and brand new rubber industrial gloves. For more grip and unscrewed both focusers. To discover an identical M95 [?] thread on both. Off with one and straight on with the next. My 102mm APO now sports an identical focuser but a Feather Touch instead of the original. The nominal 2.5" with 90mm drawtube movement have the same sized fittings! 

 It gets even better: The Feather Touch focuser is shorter than the Tecnosky by a whopping 50mm! When fully racked in. The same will be true for all the other 102mm f/7 FPL53 APO clones of course. 

 Which means 50mm more inward travel from focus. Binoviewing without a GPC or Barlow! While simultaneously allowing a wider range of diagonals, solar wedges, etc. Yet to be confirmed in practice but almost certainly true. Being able to use a focuser I already own is just a bonus. One less item to dispose of.

 More inward travel might mean a donor Lunt 60MT etalon. Can be ideally placed in the light path of an f/7 refractor. My f/7 refractor? Without having to saw a length off the main, telescope tube. We'll see. 

 I bored out an Omegon, 35mm extension to 52mm to a depth of 28mm. With the active length of the extension being 35mm. The added physical [optical path] length is only 7mm. It occurs to me that I could gain a further 10-12mm. By boring out the 2" push fit Feather Touch adapter to 52mm push fit. This has an M63 male thread and is only 19-20mm deep. The same adapter on the Tecnosky is 38mm deep. So there is nothing to be gained there. 

 The magic number we are looking for is 264mm spacing between the etalon and the focal plane of the telescope. The native focal length of my telescope is 714mm. The shortest I can make the telescope/focuser/etalon adapter is around 520mm. That still leaves 194mm. Even using the FT focuser and my mods to various parts leaves a shortage of 70mm. Which is not nearly enough for optimum etalon tuning. The 264mm figure is set by the power of the lenses in front of and behind the etalon. Which are supposed to send parallel light through the etalon. Then converge the exiting beam as if nothing was there.

 M63 is a fairly common thread size. I'll see what else is available in a thinner format. Telescope-Service sells an M63mm male adapter to 2" push fit for €61. At a fraction of the cost of the Starlight original. The T-S example might be considered preferable to chucking a €230 part in the lathe! One slip and ouch! 

 It would be possible to remove a focuser completely from the equation. Just find an M96 male threaded part to fit the main tube. RAF do a thin, double ended M96 male ring. Then you just need to add whatever is required to make up the missing 50mm. I suppose a 3D printer could manage a shallow flange with a male 96mm thread and 52mm internal bore. Or something suitable for holding a 52mm clamping ring. M63?

 Hang on! I have a ready made, threaded rotation ring on the Tecnosky focuser. Removing the centering screws will provide a fitting to go in the end of the main tube without a focuser. Or, leave the inner ring in place and unscrew the focuser body. Done. 

 There is a male M81 thread on the back of the inner ring. Where the focuser body fits. The two nested rings have a depth of only 26mm. More than enough shortening to fit the etalon. Now I need a 2" push fit adapter to fit the M81 male thread. Prima Luce make an M81 adapter but it only reduces to M63 male and costs over €100! Telescope-Service has hundreds of adapters but no M63 female to female connector to add the M63 to 2" eyepiece receptacle. Which would still need to be bored to 52mm for the etalon nosepiece. 

I could turn plain adapters on my lathe but not the fine threads used on telescopes. Ideally there would be an M82 female to M63 female adapter. That would use the Tecnosky focuser fittings. Without the focuser body. I could turn a doughnut ring to accept the Omegon extension but that can't be copied by others. I was hoping for a commercial plug 'n' play solution. 

 UPDATE: I'll delete most of this text after some editing. The image shows the way forward. A simple adapter sleeve. Using the original V-grooves of the Feather Touch focuser and the Lunt 60MT etalon housing. 

  

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