21.02.2020 New 6" f/10 H-alpha + Cloud and rain!

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Friday: 38-42F Blue skies! An hour of early sunshine but it is clouding over now. I'm struggling to get an image with the new telescope and the camera. The view through an eyepiece is like tunnel vision. I've dismantled the stack but there is nothing unusual or out of place. Double checked the focus and etalon distance. All seems okay. I'll be trying to view between the clouds now.

The problem was reaching inward focus. With so much cloud racing across the sun I am getting only a fraction of a second of sunshine to make adjustments. With the brightness level all over the place I can't focus at the same time.

I have removed the helical focuser and fitted a shorter extension. I have also shortened the first extension at the back plate. To try and throw the focal plane further out. The etalon group can act as a weak Barlow in this respect. Luckily, I have a 2" x 2" x 37mm long, Baader Click-Lock adapter on order to act as the first extension in the back plate. Otherwise it's a matter of shortening the OTA's main tube. My shortest 2" Ø extension doesn't have a 2" thread for the protective UV/IR blocking filters. Which pushes the etalon outwards if I fit them to the AOK etalon adapter.

Meanwhile the cloud is getting denser and heading for full overcast and even a hint of rain! It is getting windy in the dome now. I might as well give up for today!

Saturday 42F, overcast, heavy rain and severe gales gusting to 60mph. I had better batten down the hatches again. Or, rather, tie down the dome. The westerly gusts were fierce as I secured the dome and mounting with ratchet straps. Prodigious quantities of rain are falling almost horizontally. I emptied my half full collection tubs and covered the mounting with a tarpaulin. Well secured with cords at every eyelet.

The parking space is covered in standing water and the drive is running like a stream! The worst I have seen it in over 20 years. Typical! I secured the observatory in time for the supposed 55+mph wind to drop to nothing and the rain to stop. Sunshine out of clear blue skies anybody?

 I ought to have the ratchet straps permanently stowed on the dome if these gales are to continue for months on end. Not sure, yet, how to store them to follow a concave surface. The pulley system uses screw hooks on the ribs to keep the thing tidy.

Hooking the straps onto eye-bolts at the top of the dome does not easily lend itself to a cleft stick. Keeping even my compact, sliding/telescoping stepladder permanently in the dome is tiresome. I suppose I could support the ladder on hooked brackets on the octagon's top ring. So the ladder stands upright and well clear of the floor. So my huge winter boots can easily negotiate the invisible obstacle when I am not looking out for it. I hardly ever use the doors to the veranda. So the ladder could go at the top of the stairs behind the trapdoor. Providing a further layer of security against the bipedal rodents.

There is the promise of some sunshine tomorrow morning. Will he be able to reach inward focus? Or will he have to re-cut the main tube first? Read tomorrow's exciting episode! 😎

Sunday: 41F. Wall to wall cloud but still no rain by 10.00. It started raining the moment I opened the dome shutters to get more light! I removed the 6" OTA in preparation for fitting the 7" beside it on new crossbars across the saddle. I am using 3/4" multi-plywood, 80mm x 345mm, for the crossbars to save wasting precious, scrap aluminium for the first trial.

The saddle had to come off the Dec axis to drill larger, 8mm, fixing holes for the cross bars and tube rings. I didn't want swarf all over the mounting, RA wormwheel and floor.

I'm going with a 10cm/4" offset for the 7" and just over 6" offset for the 6". 20kg : 12kg. It is important to balance the pair around the Declination axis. By arranging their moments to be equal there should be no asymmetric imbalance. The images show today's progress. I manged to get both OTAs mounted before I fitted the 7" objective. The extra weight would have made mounting the 7' long OTA even more difficult. 

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