My play with trying to utilize my old PST DS etalon yesterday ended up a bust, so I'm back working on the 102mm f10 which is stopped down with a 82mm red #25 as an ERF.
When I measure to the forward edge of the rubber band on the tuning ring should I measure from the front, center, or rear of the OG to get the most desirable separation?
Objective/ etalon separation
Re: Objective/ etalon separation
If you're trying to find the -200mm position for the etalon John, measure 200mm forward from the focal point to the front of the rubber tuning ring. If you already have the measurements then I guess from the centre of the OG is best.
Allan
- Merlin66
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Re: Objective/ etalon separation
What Allan says.....
IMHO I would find the exact focus by focusing an image of the sun on a piece of card and measuring back to the rear edge of the OTA.....
IMHO I would find the exact focus by focusing an image of the sun on a piece of card and measuring back to the rear edge of the OTA.....
"Astronomical Spectroscopy - The Final Frontier" - to boldly go where few amateurs have gone before
https://groups.io/g/astronomicalspectroscopy
http://astronomicalspectroscopy.com
"Astronomical Spectroscopy for Amateurs" and
"Imaging Sunlight - using a digital spectroheliograph" - Springer
https://groups.io/g/astronomicalspectroscopy
http://astronomicalspectroscopy.com
"Astronomical Spectroscopy for Amateurs" and
"Imaging Sunlight - using a digital spectroheliograph" - Springer
Re: Objective/ etalon separation
There's a close relationship between those 2 distances.
This afternoon I changed OG/etalon spacing to read off the center of the OG, that required a matching change in focuser travel.
Depending on weather I might make a change from the rear of the OG, but I expect the same final results.
Seeing has just been atrocious so it's tough to do much.
And I expect I'm going to be faced with what I consider poor focus and sharpness till I can finally get a DERF and replace that red glass I'm using now.
This afternoon I changed OG/etalon spacing to read off the center of the OG, that required a matching change in focuser travel.
Depending on weather I might make a change from the rear of the OG, but I expect the same final results.
Seeing has just been atrocious so it's tough to do much.
And I expect I'm going to be faced with what I consider poor focus and sharpness till I can finally get a DERF and replace that red glass I'm using now.
- Merlin66
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Re: Objective/ etalon separation
John,
When you measure (re-measure?) the focal point and position the front of the PST knurled ring at -200mm, I'm sure (based on over 100 successful mods, so far) that you'll be cooking with gas.....
When you measure (re-measure?) the focal point and position the front of the PST knurled ring at -200mm, I'm sure (based on over 100 successful mods, so far) that you'll be cooking with gas.....
"Astronomical Spectroscopy - The Final Frontier" - to boldly go where few amateurs have gone before
https://groups.io/g/astronomicalspectroscopy
http://astronomicalspectroscopy.com
"Astronomical Spectroscopy for Amateurs" and
"Imaging Sunlight - using a digital spectroheliograph" - Springer
https://groups.io/g/astronomicalspectroscopy
http://astronomicalspectroscopy.com
"Astronomical Spectroscopy for Amateurs" and
"Imaging Sunlight - using a digital spectroheliograph" - Springer
Re: Objective/ etalon separation
Oh yeah, been there. That paper you put together years ago is still my main source of info when I'm trying to figure what gives.
This is a bad time to be doing this stuff.
Low Sun, short days, and constant storms take away all the fun.
This is a bad time to be doing this stuff.
Low Sun, short days, and constant storms take away all the fun.
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Re: Objective/ etalon separation
This is a bad time to be doing this stuff.
Low Sun, short days, and constant storms take away all the fun.
Hi John
I'm very much with you
Low Sun, short days, and constant storms take away all the fun.
Hi John
I'm very much with you
Only stardust in the wind, some fine and some less fine scopes, filters and adapters as well. Switzerland 47 N, 9 E, in the heart of EUROPE
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from 7 am - 7 pm http://www.nanosys.ch
from 7.01 pm - 6.59 am http://www.wastronomiko.com some times vice versa