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Emanuele
Lord of the Ring
Reged: 11/19/03
Posts: 4967
Loc: almost Colorado
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Hi all!!
Quick question about imaging through my Zeiss telementor!
First of all, only a quarter or little less of the solar disk can fit in the FOV of my DMK thorugh the Telementor!! Is there a Focal reducer that can help me fit the whole disk?
Secondly, how do you guys know you are in focus or not? I cannot see any detail while looking to the video window on my Macbook! Just a grey sun!
All this is using my Zeiss SFO63 filter!
Thank you for the help!
E.
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http://www.backyardskies.com
TEC140 #393 --- Vixen VC200L w/FeatherTouch --- Takahashi EM400
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Andy D
sage
Reged: 12/03/06
Posts: 207
Loc: Taranaki, New Zealand
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Hi Emanuele,
Finding focus in WL photography without a sunspot will be tricky, the best you'll be able to do is to try to get the limb sharp. I don't know when you were imaging, but there may simply not have been a sunspot there to focus on. I'm assuming that you had a mid grey sun, and were not over or under exposed,(around a '170' brightness setting for an 8 bit camera)
Some people use the ATIK focal reducer or similar. I generally prefer to zoom in on a feature of interest, but I appreciate that there are people who like the full disk view. To get the full disk you can either use a FR as you've suggested, use a larger chip camera, or make a mosaic.
You can calculate what the Field of View (FOV) of your camera will be using :
FOV (in °) = 57.3 x camera chip size / focal length where the same units are used for chip size and FL
For example if you had a DMK 21 with a 640x480 array of 5.6 micron pixels, then you'd have a 3.58 x 2.69mm chip and so with say your Telementor of 840mm FL, you'd have a FOV of 14' x 11'
Or if you had a DMK 41 with a chip of 1280 x 960, 4.65 micron pixels, then you'd have a FOV of 24' x 18'
You could maybe use your DMK for 'close up's' of sunspots, and maybe a digital SLR camera (without the lens) for the full disk shots. You might well find that you get better WL images while using a green filter with your Telementor, a #56 for example.
andy
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http://pbase.com/andy_dodson
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Emanuele
Lord of the Ring
Reged: 11/19/03
Posts: 4967
Loc: almost Colorado
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Andy,
thank you so very much!!!
Yes, I do have the DMK21 and a Canon 40D as well so I guess I am covered both sides!
I did not know that I could attach the 40D to the Telementor!!! I have had so much trouble getting the Telementor to reach focus and still I cannot seem to be able to reach focus with a 2" diagonal!!
How can I attach the 40D to the Telementor for prime focus photography? That would be great!!!
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http://www.backyardskies.com
TEC140 #393 --- Vixen VC200L w/FeatherTouch --- Takahashi EM400
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Andy D
sage
Reged: 12/03/06
Posts: 207
Loc: Taranaki, New Zealand
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Hi Emanuele,
I don't know if the Telementor has sufficient back focus to allow a 40D to reach focus, you'd just have to try it and see I guess. I do know though, that you'd get better results if you image *without* the diagonal, that's one less source of abberations you can eliminate. (this is for WL photography and doesn't refer to Ha imaging where the diagonal is often required as it incorporates a blocking filter) And the diagonal is robbing you of precious back focus of course.
andy
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http://pbase.com/andy_dodson
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Ralph Marantino
Postmaster
Reged: 05/01/05
Posts: 6330
Loc: Old Bridge, New Jersey
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My 63 mm Telemator reaches focus with a Zeiss 2 inch diagonal but the diagonal is a prism and cost me 450 dollars. 
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Lunt H-alpha LS100THa/B3400
Rockland Astronomy Club
Member BAA Solar Section
Central Appalachian Astronomy Club
Astronomical League
DSPST,PST & 70mm Coronado Cal K telescope.2.2A
Zeiss 2 inch prism diagonal&Zeiss Zoom EP
2inch APM Herschel Wedge in a 94mm F7 Brandon
14.5 inch f4.2 Starmaster Dob(Zambuto mirror)
TeleView Genisis SDF with 1000 Oaks Glass filter
Zeiss 63mm f13.5 refractor 1000 Oaks Glass filter
Itty Bitty Solar Radio Telescope.
LHRIES Lite Solar Spectrometer
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