nytecam
Post Laureate
Reged: 08/20/05
Posts: 4755
Loc: London UK
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Finally got a clearish night to test my Meade DS-2114 [114mm f/8 Jones-Bird Newt] converted to a modified Lensless Schmidt camera [LSC] on starlight as below although image quality more to do with vagaries of the Meade altaz drive system  Normally a LSC has the detector/film within the main tube but I've used the existing Newtonian secondary to project the image deep within the regular rackmount focuser - Barlow-like Jones-Bird 'corrector' lens was removed as a LSC has only one optic eg the oversized primary mirror.
I've yet to test the larger 90mm aperture-stop on starlight. More samples to follow 
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Nytecam 51N 0.1W
Meade 30cm LX200+ETX-70+DS-2090+C8+Ha+CaK PSTs SBIG SGS+homebuilt spectrographs
Starlight SXVF_M9/Lodestar/Canon 300D DSLR/Fuji E550
My observatory build-ETX-70 imaging-spectro page
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nytecam
Post Laureate
Reged: 08/20/05
Posts: 4755
Loc: London UK
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Here's M13 in SX camera full res in 10s exp [2x5s] which show pretty good star images with perhaps some vertical trailing Co-adding images taken 20-30s apart starts to show field rotation via the AltAz mount
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Nytecam 51N 0.1W
Meade 30cm LX200+ETX-70+DS-2090+C8+Ha+CaK PSTs SBIG SGS+homebuilt spectrographs
Starlight SXVF_M9/Lodestar/Canon 300D DSLR/Fuji E550
My observatory build-ETX-70 imaging-spectro page
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rutherfordt
super member
Reged: 05/07/06
Posts: 105
Loc: Blountville, Tennessee USA
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Nytecam:
I'm following your experiences with this with interest-- I have been planning for some time to do something like this, but I haven't actually assembled mine.
I have a 4.25-inch f/2.6 mirror that I am planning to use for this purpose. Like you I am also planning to use a small secondary mirror to send the image to the outside of the tube so that I can get a camera there.
The steep light cone of the mirror, though, means that I will need to have a large secondary in order to get the focal plane out to the edge of the tube. This means that the secondary will block most of the mirror once the aperture stop is installed so things may not be practical with a mirror this small.
I am not concerned about pinpoint star images as I was planning to use it for photometry. Pinpoint stars are to be avoided there.
I guess that I need to sit down and put this thing together and see what happens-- maybe it will surprise me.
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Tom Rutherford
10-inch f/6 Homemade Dobsonian (Cave mirror)
8-inch f/6 Homemade Dobsonian
6-inch f/5 Meade SN6
6-inch f/10 Celestron C6
5.5-inch f/3.6 Celestron Comet Catcher
66mm f/6 WO Petzval
2-inch f/15 Nippon Kogaku (my first telescope)
assorted unassembled pieces and parts
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nytecam
Post Laureate
Reged: 08/20/05
Posts: 4755
Loc: London UK
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Hi Tom -thanks for your interest Quote:
I have a 4.25-inch f/2.6 mirror...Like you I am also planning to use a small secondary mirror to send the image to the outside of the tube so that I can get a camera there.
Focus seems very critical and an external rackmount is perhaps the way to go. Effectively each star is illuminated by a donut of light and a larger central obstruction 'kills' the camera speed below the nominal f/ratio.Quote:
I am not concerned about pinpoint star images as I was planning to use it for photometry. Pinpoint stars are to be avoided there.
Indeed they are for that application Quote:
I guess that I need to sit down and put this thing together and see what happens-- maybe it will surprise me.
My results [re stellar sharpness] have surprised me and maybe relaxed slightly via a larger [and thus 'faster'] aperture stop
I should clarify that my Lodestar CCD is quite tiny [in Schmidt camera terms] some 6.5 x 4.75mm with 8 micron pixels so although field curvature at the focal plane can be ignored, the high pixel resolution is more testing on the overall system which so far, on these initial experiments, proves adequate.
The final pic of the session eg M57 in 10s single exposure - the mag 15 central star was there on most of the untrailed images. Good luck with your project and keep us posted
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Nytecam 51N 0.1W
Meade 30cm LX200+ETX-70+DS-2090+C8+Ha+CaK PSTs SBIG SGS+homebuilt spectrographs
Starlight SXVF_M9/Lodestar/Canon 300D DSLR/Fuji E550
My observatory build-ETX-70 imaging-spectro page
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nytecam
Post Laureate
Reged: 08/20/05
Posts: 4755
Loc: London UK
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Here's Vega on a focusing test - diffraction spikes from 3-vane secondary support plus central [vertical reinforcing] 'bar' on the 75mm aperture-stop
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Nytecam 51N 0.1W
Meade 30cm LX200+ETX-70+DS-2090+C8+Ha+CaK PSTs SBIG SGS+homebuilt spectrographs
Starlight SXVF_M9/Lodestar/Canon 300D DSLR/Fuji E550
My observatory build-ETX-70 imaging-spectro page
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jeffg
member
Reged: 02/13/07
Posts: 40
Loc: Irvine CA
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I've started to regularly use a lenless Schmidt for photometry. It is made from a chipped C-8 mirror I picked up. I chose a .003 inch blur circle which gives an aperture of 4.5 inches. I use a 2.14 inch diagonal to kick the light out to a DSI-Pro in the focuser. It's a fast F/3.5 system, that has almost a 50% obstruction, but works very well. Attached is an image of V Bootes (brightest star on the right). There are also several check stars in the image.
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Jeff
14", 10", & 4.25" Dobs
8" Schmidt Newtonian, C-8 SC, 8" LSC
6" Cave Student Model A, 6" Dall-Kirkham, 6" RV-6
5" Refractor & 80 mm Folded Refractor
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nytecam
Post Laureate
Reged: 08/20/05
Posts: 4755
Loc: London UK
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Nice one Jeff  Do you have a picture of your setup and how sensitive is the camera eg how faint in what exposure? I'm getting down to mag 13/14 in 10s exposure with mine and the images seem potentially round to the corners of the field
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Nytecam 51N 0.1W
Meade 30cm LX200+ETX-70+DS-2090+C8+Ha+CaK PSTs SBIG SGS+homebuilt spectrographs
Starlight SXVF_M9/Lodestar/Canon 300D DSLR/Fuji E550
My observatory build-ETX-70 imaging-spectro page
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rutherfordt
super member
Reged: 05/07/06
Posts: 105
Loc: Blountville, Tennessee USA
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Jeff:
Your image of V Boo seems to match a "D" AAVSO chart-- is that correct? What is the field of view of your lensless Schmidt? Using a 6-inch Schmidt-Newtonian and a Meade DSI Pro, I usually have to use "E" and "F" scale charts in order to get a close match to what I actually see-- you seem to have a much wider field of view (one of the advantages of a Schmidt, I know).
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Tom Rutherford
10-inch f/6 Homemade Dobsonian (Cave mirror)
8-inch f/6 Homemade Dobsonian
6-inch f/5 Meade SN6
6-inch f/10 Celestron C6
5.5-inch f/3.6 Celestron Comet Catcher
66mm f/6 WO Petzval
2-inch f/15 Nippon Kogaku (my first telescope)
assorted unassembled pieces and parts
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nytecam
Post Laureate
Reged: 08/20/05
Posts: 4755
Loc: London UK
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here's a shot of the scope with 90mm aperture stop to test with 75mm 'stop' already tested below. Finder added as Lodestar CCD has a tiny 45' x 30' fov
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Nytecam 51N 0.1W
Meade 30cm LX200+ETX-70+DS-2090+C8+Ha+CaK PSTs SBIG SGS+homebuilt spectrographs
Starlight SXVF_M9/Lodestar/Canon 300D DSLR/Fuji E550
My observatory build-ETX-70 imaging-spectro page
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jeffg
member
Reged: 02/13/07
Posts: 40
Loc: Irvine CA
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For the AAVSO chart, I originally printed out the "A" chart, but then to the DSS image to ensure I was on the right field. One reason I picked V boo was that is was close to a bright star that was easy to find. And V boo shows up both in the Meade Autostar star charts and "The Sky". That way I could "go-to" it easily. The FOV using the Meade DSI-Pro is supposed to be about 40x31 arc minutes, but I've never measured it. The main reason for the large FOV is short focal length. Since I used a C-8 primary, the focal length of the system is only 16 inches. That puts the RC out at 32 inches where the 4.5 inch aperture stop is.
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Jeff
14", 10", & 4.25" Dobs
8" Schmidt Newtonian, C-8 SC, 8" LSC
6" Cave Student Model A, 6" Dall-Kirkham, 6" RV-6
5" Refractor & 80 mm Folded Refractor
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jeffg
member
Reged: 02/13/07
Posts: 40
Loc: Irvine CA
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Here's a picture of my Lensless Schmidt set up in the corner of my small back yard. The image I posted previously shows about 13 magnitude in a 15 second exposure. It was taken with a photometric visual (V) filter in place, so that cuts some of the incoming light. Since I live in a very light polluted part of southern California (limited magnitude on a average night is 3.4), I'm somewhat limited to what stars I can take data on without driving for a couple of hours. 
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Jeff
14", 10", & 4.25" Dobs
8" Schmidt Newtonian, C-8 SC, 8" LSC
6" Cave Student Model A, 6" Dall-Kirkham, 6" RV-6
5" Refractor & 80 mm Folded Refractor
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nytecam
Post Laureate
Reged: 08/20/05
Posts: 4755
Loc: London UK
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Thanks Jeff - excellent and informative work and invaluable pic of your Lensless Schmidt camera - well done
Light pollution - tell me about it - my skies are the same but tested scope on moon last night [via 90mm stop = nominal f/5] to demo the fov of my LSC thus.
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Nytecam 51N 0.1W
Meade 30cm LX200+ETX-70+DS-2090+C8+Ha+CaK PSTs SBIG SGS+homebuilt spectrographs
Starlight SXVF_M9/Lodestar/Canon 300D DSLR/Fuji E550
My observatory build-ETX-70 imaging-spectro page
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jeffg
member
Reged: 02/13/07
Posts: 40
Loc: Irvine CA
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Nytecam:
Nice moon shot. You seem to have a very wide FOV with your LSC. I notice you've done quite a bit of spectroscopy. That's something I think I'd like to move into one of these days as there are some reasonable spectroscopes available. My brother is currently doing some testing with a simple grating, which seems to work for brighter stars in an uncrowded star field.
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Jeff
14", 10", & 4.25" Dobs
8" Schmidt Newtonian, C-8 SC, 8" LSC
6" Cave Student Model A, 6" Dall-Kirkham, 6" RV-6
5" Refractor & 80 mm Folded Refractor
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nytecam
Post Laureate
Reged: 08/20/05
Posts: 4755
Loc: London UK
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Quote:
Nice moon shot. You seem to have a very wide FOV with your LSC.
My LSC 450mm fl and SX Lodestar cam data here. Quote:
I notice you've done quite a bit of spectroscopy. That's something I think I'd like to move into one of these days as there are some reasonable spectroscopes available. My brother is currently doing some testing with a simple grating, which seems to work for brighter stars in an uncrowded star field.
The easiest route is to use a Rainbow Optics or Staranalyser transmission grating immediately before the CCD as my webpage - just swap-out your photometric filter for screw-in grating and no other complex reimaging optics needed It works even in a crowded starfield as my lo-res nova/VS spectra show on above website.
There are plenty of cheap gratings around but they are usually very inefficient in forming a spectrum - hence the reference to Rainbow and Staranalyser gratings which are excellent - see Staranalyser Yahoo Group and good luck.
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Nytecam 51N 0.1W
Meade 30cm LX200+ETX-70+DS-2090+C8+Ha+CaK PSTs SBIG SGS+homebuilt spectrographs
Starlight SXVF_M9/Lodestar/Canon 300D DSLR/Fuji E550
My observatory build-ETX-70 imaging-spectro page
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dongchina
member
Reged: 08/19/08
Posts: 10
Loc: Tianjin, CHINA
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Nytecam:
I have a Newtonian D=114 f=900.And I want to convert it to LSC. I do not know what they are? [see the pic. pointed by red lines] I take photos by 35mm film SLR,not a CCD. How and what shall I do?
And must I remove the 2nd mirror away or keep it at its original place and do some adjustment?
I find MG@wpo.uk. Is this your e-mail address? Are you the writer, Mr. Maurice Gavin, of the paper of Lensless Schmidt Camera?
Now I will do an experiment on the cheap 114. If it succeeded, I will do a larger one, for I can find D=300mm primary mirror and length is 500mm barrels. But I confuse that which kind of primary mirror is the correct one? paraboloid or sphere??
Please give me some help~~~ 
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I am an amateur astronomer in Tianjin, CHINA. I hope that I could make good friends with you here. And to enjoy the beautiful sky & universe together......
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dongchina
member
Reged: 08/19/08
Posts: 10
Loc: Tianjin, CHINA
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i can not add photo & pictures here.~~~ how to do???? help me~~~ Which button shall I point???
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I am an amateur astronomer in Tianjin, CHINA. I hope that I could make good friends with you here. And to enjoy the beautiful sky & universe together......
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Joe Cipriano
Entropy Personified
Reged: 09/03/05
Posts: 3830
Loc: Uh... anyone have a GPS?
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Dongchina:
Welcome to CN.
If the image is on your computer: Type in the text part of your post, make sure the "I want to preview my post and/or attach a file" checkbox is checked, then hit the "Continue" button. The next page displayed will show your post; just below that is a text box titled "You may attach a file if you like (no bigger than 105000 bytes please).", with a Browse button opposite. Click on the Browse button, and find the image file on your computer that you want to post. When done, click on the "Ok, submit" button.
Your image must be 800 X 800 pixels or less, and 100Kb or less.
Hope this helped.
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In the Land of Eternal Light Pollution & Great Pizza (Chicago)
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CGE (way modified)
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