Back after a tough absence

Frankenscope? Let's see it!***be advised that NOTHING in this forum has been safety tested and you are reading and using these posts at your own peril. blah, blah, blah... dont mess around with your eyesight when it comes to solar astronomy. Use appropriate filtration at all times...
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JohnM
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Back after a tough absence

Post by JohnM » Fri Oct 20, 2017 11:03 pm

Back after a long absence, old age BS, eyes heart yada yada; this getting up to 75 is such a crock.
Anyway, I can see some now with one eye and I can get around much better, so it's back out to the observatory blowing the dust off things.
Got the old NGT 12.5 up and running and now it's back to my stage 2 PST mod mod. :D

I've misplaced my notes etc, and am setting up with the Denk 60 mm objective I hung onto.
My focuser, etalon, BF, EP assembly is still all together. I just need to know where to measure for the rest of the OTA,
From front of the etalon to front of the objective is correct, right?

I did a little experimenting the last couple days. I could get excellent resolution of proms showing now and just barely could bring a large filament that's been showing on the Solar surface into view, but not much surface detail at all.
My sweet spot is way off center and once I'm sure of the correct distance out to the objective I probably should check the collimation again.

Anyway, TIA, for any help you can give this old fart.

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Merlin66
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Re: Back after a tough absence

Post by Merlin66 » Sat Oct 21, 2017 5:12 am

John,
Glad to hear you are still with us!!
The etalon should be positioned as close as possible to -200mm inside the prime focus.
Remind us, what is the donor scope??
"Astronomical Spectroscopy - The Final Frontier" - to boldly go where few amateurs have gone before
https://groups.yahoo.com/neo/groups/ast ... scopy/info
"Astronomical Spectroscopy for Amateurs" and
"Imaging Sunlight - using a digital spectroheliograph" - Springer

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marktownley
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Re: Back after a tough absence

Post by marktownley » Sat Oct 21, 2017 11:48 am

Good to have you back John!
Image
http://brierleyhillsolar.blogspot.co.uk/
Solar images, a collection of all the most up to date live solar data on the web, imaging & processing tutorials - please take a look!

JohnM
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Joined: Fri Apr 20, 2012 2:06 pm

Re: Back after a tough absence

Post by JohnM » Sat Oct 21, 2017 12:59 pm

Hello old friends, the last few years were not a lot of fun, I had to give up a lot of things; long range target shooting, flying RC planes, etc., but I can still drive. Only during the day.
The scope "was" the 60 mm Denkmaier upgrade from some years ago. My sample never worked. could never get a sharp focus.
The OTA was a strange construction made of a number of parts that all screwed together.
All I have left is the front section that holds the OG. It was supposed to be an f10.
So, I made some adapters to be able to connect my "200 mm focuser unit" at 400 mm from the OG.
Now I remember what I forgot to do. Actually get a measurement of the distance to a focused image on a target.
If the Sun comes out today, I'll set up and get a measurement to a sharp focused image of the Sun and then get my position for the etalon.
I'm using my old Antares SCT focuser with adapters to hold the Etalon to the EP to get that 200 mm I need there.
If I can get the thing to work decently I'll look at finding a piece of new aluminum tube to put together a proper 1 piece tube. I think I have all the parts in the shop to do it, just take some time to fab it up.

I've noticed in some recent reading some guys have been getting good results stacking 2 PST etalons, now that would be interesting and somewhat affordable with this 60 mm. I have 6" and 4" achros that would make good doner scopes, but the cost of the DERF is just too much to go that route right now.

JohnM
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Re: Back after a tough absence

Post by JohnM » Sat Oct 21, 2017 3:32 pm

OK. I got focus at 630 mm instead of 600, I bet that figure is somewhere in that stack of notebooks in the observatory. :)
Now I need to readjust the tube length. Front of etalon there? That 630 mm was measuring from front of OG.
There's such a bitter wind this morning the wind chill is in the low 20's degree F, with the wind swirling around in the obs with the roof open. Pretty miserable out there.

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