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Wednesday 9th. 36F and blowing a northerly gale. With sunny periods to play with I tried various set-ups. The seeing was poor with serious boiling along the sun's limb in H-alpha. A small prominence sat on the bottom of the sun in my binoviewer view but I could see no surface markings. Nor in white [green] light in the 7".
Yesterday's talk of trapping the PST filter barrel between a 2" : T2 adapter and a cheapo helical focuser was only an illusion. The barrel was sagging except in one position of the focuser. Rather than waste precious solar time, by turning a metal support tube, I temporarily used a plastic bottle top with a suitable hole saw [35mm] drilled in the middle.
Today I was getting poorer images than before. So I carefully measured the distance of the rear of the PST Etalon ring to the focus of the 6" F/8 objective. I find this easier with a dark piece of card and a steel rule. White paper or card is too bright and spoils the view of the sharply focused solar disk.
It was supposed to be 200mm but measured 225mm or an inch too much! Which meant I had to add to the Celestron's main tube or add a 1" spacer. Rather than what I did. I scratched a ring around the tube using an old vernier caliper and marked the three fixing holes for the tailpiece. Hoping to reach focus with a star diagonal and binoviewer.
Then I hack-sawed off the 1" wide ring from the main tube. The tube had been chopped by a previous owner for imaging but I had no idea by how much. I just remember telling him that I couldn't reach focus. He suggested I try a star diagonal and that was enough.
That's as far as I have reached this morning as I pause for lunch. The cloud has now cleared as I prepare to return to the fray but the sun is already sinking fast below the ridge of my house to the south.
After lunch I discovered I still couldn't reach focus with the binoviewer and 1.25" star diagonal. So I recovered from my major faux pas by swapping a 40mm x 2" extension for one 80mm long in the tailpiece backplate. I have recovered all but 10mm of my error and can easily overcome that small difference. The telescope looks better with a longer extension in the backplate. I prefer the traditional stepped sized tubing at the tail end of a telescope. A 3.5" Starlight Feather Touch refractor focuser on the 7" would do very nicely but is an expensive luxury when I already have an old Vixen 2" focuser.
I must have been having a brain freeze when I measured twice [well three times] and then cut the main tube [only once.] It really needed to be longer to shorten the distance between the PST etalon and the focus of the CR150 objective. By chopping the main tube I actually doubled my error.
I went through all of this late last winter. That was before somebody, far more experienced, pointed out that the REAR of the PST ETALON BAND should be 200 mm INSIDE FOCUS.
I have typed this out to ensure I can find it again after wasting valuable time on the laptop searching through my old posts to confirm my hazy memory.
It was blowing a gale all day and only just crept up to 40F in the dome. I was perfectly comfortable in my usual, scruffy assortment of winter clothing and never even bothered to close up my old, down jacket all day. It is certainly breezy in the dome whenever there is any wind. I shall have to do something about that and soon.
After lunch I discovered I still couldn't reach focus with the binoviewer and 1.25" star diagonal. So I recovered from my major faux pas by swapping a 40mm x 2" extension for one 80mm long in the tailpiece backplate. I have recovered all but 10mm of my error and can easily overcome that small difference. The telescope looks better with a longer extension in the backplate. I prefer the traditional stepped sized tubing at the tail end of a telescope. A 3.5" Starlight Feather Touch refractor focuser on the 7" would do very nicely but is an expensive luxury when I already have an old Vixen 2" focuser.
I must have been having a brain freeze when I measured twice [well three times] and then cut the main tube [only once.] It really needed to be longer to shorten the distance between the PST etalon and the focus of the CR150 objective. By chopping the main tube I actually doubled my error.
I went through all of this late last winter. That was before somebody, far more experienced, pointed out that the REAR of the PST ETALON BAND should be 200 mm INSIDE FOCUS.
I have typed this out to ensure I can find it again after wasting valuable time on the laptop searching through my old posts to confirm my hazy memory.
It was blowing a gale all day and only just crept up to 40F in the dome. I was perfectly comfortable in my usual, scruffy assortment of winter clothing and never even bothered to close up my old, down jacket all day. It is certainly breezy in the dome whenever there is any wind. I shall have to do something about that and soon.
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