bcjolly
member
Reged: 09/18/05
Posts: 38
Loc: North Carolina, USA
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Hello to All,
I am new to CN, but have been perusing the forums for some time. My question: "How long of an exposure can one expect to make with a 'polar-aligned' Takahashi EM-200 before the image starts to suffer?" Thanks! Keep lookin'up.
Barry C. Jolly
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s2jesse
super member
Reged: 01/17/05
Posts: 123
Loc: Sonoma County, CA
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It just depends on how well its polar aligned. If you drift align im sure pretty long. Ive never used that mount but ive gotten about 3 minute exposures with 0 trails just rough alinging. Ie 1 star alightment with an lx200 f10. Im sure thats just plain luck though.
however your best bet is to drift align and then guide / autoguid.
Jesse
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Jesse Hayes
Paramount MX
FSQ106EDX
10" LX200 GPS UHTC
Orion ED80
SXH694
T2i unmodded
5DMKii unmodded
300D Modded
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Radek
super member
Reged: 05/30/05
Posts: 130
Loc: Prague, Czech rep.
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It will depend on two things:
- P.E. of the mount
- focal length of the telescope
Radek
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Dean
Postmaster
Reged: 12/31/04
Posts: 5431
Loc: Bailey Co Elev 8780 feet
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The EM-200 has very little PE, so it comes down how well your alignment is, the FL of your scope, the pixel size of your camera and what you consider "suffering". I always autoguide mine, but I have seen unguided images with exposures of 5 minutes with a FL of about 500mm that looked pretty good. At that FL the PE translates to an error something like 1-2 pixels (depending on the CCD), so at 1000mm FL, the error is something like 2-4 pixels. Some might consider that tolerable (I wouldn't).
But why not guide? A well aligned, guided EM-200 with a reasonable payload (up to maybe 20-25 pounds) will be dead on all night long. I've imaged with exposures as long as 30 minutes at 820mm - here is an example of the Horse Head in Ha that is 2 hours worth of 30 minute exposures guided.
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"Don't sweat the petty things and don't pet the sweaty things" - George Carlin
deanrowe.net/astro
Whats with that avatar?
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Chris Graham
mmmm...Haggis
Reged: 04/01/04
Posts: 4886
Loc: Stirling, Scotland
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Take a look at my site, i dont guide, only roughly polar align and so far my images are not too bad.
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-Skywatcher 8" Reflector on HEQ5 with Skyscan
-Orion ED80 Refractor
-70mm Guidescope/grab and go scope
-Canon EOS 350D
-Toucam Pro 2
Astronomy & Veggies
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bcjolly
member
Reged: 09/18/05
Posts: 38
Loc: North Carolina, USA
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"Thank you!" to all who replied to my query. I am a railroad engineer who is anticipating retirement next August. I have always loved space and space related science, hence my interest in Astronomy and Astrophotography. My first telescope was a used Meade LX-200 12" SCT bought about two years ago. I tried taking pictures with it using a Sony 707 DSC. Not much success. I then began reading forums on CN and as a result bought a Takahashi FS-128 with the EM-200 temma 2 mount. I also bought a Canon 350DXT Huteck modified DSLR. I have tried a few photos of M 42 and M 45. They were much better than with the SCT/Sony setup. However, they are not up to the quality seen on this forum. My new-ness to this part of science is the reason for asking about unguided photography. With my expenditures thus far, I don't have the finances to purchase a guide camera and will just have to make do for a while with what I have. While I may not have everything needed to take good images, I have tried to comply with the advise of this forum's members and buy good equipment to start with. Thanks again to all who replied. I will be back with more questions. Please be patient with me as I have a lot to learn and must start from the ground up.
Sincerely,
Barry C Jolly
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Radek
super member
Reged: 05/30/05
Posts: 130
Loc: Prague, Czech rep.
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Well, you have excellent equipment, and regarding guiding, you can guide through web cam, which does not cost a lot and with some free guiding program, for example Guidedog, here is the link: http://www.barkosoftware.com/GuideDog/index.html . You will also need guidescope or off-axis guider of course. I would recommend guidescope. I think it would be pitty to take pictures and have trailed stars. You can also guide manually of course.
Radek
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ChazK
Pooh-Bah
Reged: 11/23/05
Posts: 1453
Loc: Melbourne, Florida
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Barry,
Just came accross this post. I also have a EM200 and if you drift align (from what I'm told) you should get away with 1 minute w/o guiding. My questions is how do I add a guidescope to my EM200/Tak130 setup without maxing out the weight?
Chaz
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Tak TOA 130mm/NJP Temma2
Tak FS 60CB
Canon 40D (unmodded)
Canon EF 28-135mm f/3.5-5.6
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Ptarmigan
Lagopus lagopus
Reged: 09/23/04
Posts: 3510
Loc: Arctic
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Depends. If your telescope is polar aligned accurately, you should be able to up to 15 to 20 minutes unguided. Also, shorter focal length will mean less magnification of trailing.
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Dean
Postmaster
Reged: 12/31/04
Posts: 5431
Loc: Bailey Co Elev 8780 feet
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Chaz,
The EM200 is rated at 35lbs. I know some people who have put about that much on and with careful balance, it might be doable. A Tak130 weighs what, 22lbs? That would give you maybe 10lbs to work with. Here is a picture of how I piggyback an 80mm TMB on my FS102. I have a Casady dovetail saddle I put on the EM200 that this fits on. Not counting the guide scope, all the mounting gear probably weighs 6-7 lbs, so I would guess with a similar setup you might be able to mount a guidescope weighing about 3-4 lbs.
Or you could get an autoguiding CCD and not worry about a guidescope.
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"Don't sweat the petty things and don't pet the sweaty things" - George Carlin
deanrowe.net/astro
Whats with that avatar?
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Bill G.
professor emeritus
Reged: 04/04/04
Posts: 544
Loc: Newton, NC USA
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Barry,
I have an ASGT CG-5 (Celestron Advanced Series) mount. I'm not familiar with the mount you have but my guess is that it's a higher quality than mine. The CG-5 isn't bad. I've taken 5 min shots with a 400mm fl scope (and 300D) with no visible trailing. It was with a pretty precise polar alignment. With a 2000mm fl scope (also with) 300D I've done 3 minutes with no visible trailing. That's enough exposure time to shoot quite a few different dsos, let alone with a modified 350.
It does take practice, give it time and play as much as possible.
Bill G.
South Carolina
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 I took up astronomy because I don't have time for anything else during the day.......
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ChazK
Pooh-Bah
Reged: 11/23/05
Posts: 1453
Loc: Melbourne, Florida
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Dean,
You da Man! I just ordered a new set of rings and an Orion ED 80mm. I'll let you know.
Barry,
I would look at drift alignment closer and once you have that down the PE on the EM200 should let you image just fine at f/6. Also if you have a focal reducer f/3 will let you get away with longer exposure.
Let me know how it goes. I'm experimenting with this as well.
Chaz
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Tak TOA 130mm/NJP Temma2
Tak FS 60CB
Canon 40D (unmodded)
Canon EF 28-135mm f/3.5-5.6
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tjswood
Carpal Tunnel
Reged: 05/18/05
Posts: 1881
Loc: Earth
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Dean,
I have been reading your posts (as well as others in the archives). I have been considering, and close to ordering, a Tak Mewlon 250, with an EM200 mount. I am being told by many that I will be able to image with that platform / payload, despite my skeptisism otherwise. Have asked the question to many, even those who sell them, with the answers ranging from "yes, its close but Tak numbers are conservative" to "yes definitely". Not many "no ways, don't do it" though.
The Mewlon is 27 lbs OTA and after I get it loaded up (I plan on using an SBIG 10XME) I estimate it will be > 35lbs. The Focal length is F12, as you know, and with the F9 reducer it will bring it down to 2250mm. I am still skeptical... I have an NP101 also, and plan on imaging with it also, though the EM200 or my GM8 should be able to handle that one fine.
Need all the advice I can get on the EM200 and Mewlon combo for imaging, especially if I want higher resolution. I thought about getting an NJP also... of course that would work fine for an extra $1700 and 30 lbs of mount weight...
Your thoughts are welcomed!
Tim
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tjswood
Carpal Tunnel
Reged: 05/18/05
Posts: 1881
Loc: Earth
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BTW, thought about this after I posted, sorry for the off topic post. I can delete and send a private message if it takes the thread on a tangent> 
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Dean
Postmaster
Reged: 12/31/04
Posts: 5431
Loc: Bailey Co Elev 8780 feet
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Hi Tim
I was incorrect when I said I a couple of folks who put a Mewlon 250 on an EM200 - one of those was a Mewlon 210.
The most I've put on my EM200 is maybe 22 lbs - thats gear and all, so I can't speak first hand about that much weight.
From what I've heard of loads people have put on Tak mounts - and succesfully imaged with them - I'd say it's doable, but darn close. One thing I haven't heard is how well they hold up (wear and tear wise) with those loads over time.
If it were me, I'd go with an NJP if I could. But then I'd go with an NJP if I could anyway 
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"Don't sweat the petty things and don't pet the sweaty things" - George Carlin
deanrowe.net/astro
Whats with that avatar?
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tjswood
Carpal Tunnel
Reged: 05/18/05
Posts: 1881
Loc: Earth
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Dean,
Not that it makes the decision any easier, that is definitely safe advice... I did like price, weight and portability of the EM200. But if I was in it to save a buck here and there, I probably should reconsider otherwise anyway.
I think the Mewlon will only be a part-time imager anyway, I will probably be more enticed by the NP101 because it is an easier tool to learn on, and I will be pleased with the wide fields more anyway... and the GM8 could hold that no sweat (well actually that is kinda close - even though the GM8 is "rated" at 35lbs)
You got me thinking on the whole - even the 30lb Mewlon on the EM200 for visual is going to be a load - stress on the mount is a consideration. Decisions, decisions...  haven't bought anything yet so there is still time!
I'll tell ya though, I am getting a lot of different opinions on this one!
Tim
OK, promise to take the rest to a new thread or in mail.
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Dean
Postmaster
Reged: 12/31/04
Posts: 5431
Loc: Bailey Co Elev 8780 feet
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Quote:
OK, promise to take the rest to a new thread or in mail.
I already did 
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"Don't sweat the petty things and don't pet the sweaty things" - George Carlin
deanrowe.net/astro
Whats with that avatar?
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Dean
Postmaster
Reged: 12/31/04
Posts: 5431
Loc: Bailey Co Elev 8780 feet
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Quote:
Dean,
You da Man! I just ordered a new set of rings and an Orion ED 80mm. I'll let you know.
Good luck! But be aware my FS102 which weighs 10lbs, the TMB weighs 6 and with another 6 or for rings and stuff, I'm probably right at the weight of a Tak130.
It does work well though. Here is an image of NGC 896 with that setup. Its a blend of 9 exposures of 20 minutes each in Ha and 12 of 5 minutes each of R,G & B.
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"Don't sweat the petty things and don't pet the sweaty things" - George Carlin
deanrowe.net/astro
Whats with that avatar?
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Jordy
sage
Reged: 10/25/05
Posts: 265
Loc: BC Canada
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I hope this is an ok question for this forum.
I have a nikon D70s and a DSI pro (which is still in the box). My understanding of the DSI is that it can guide a scope but only if its a Meade. Since I have a celestron Im out of luck. I saw a LPI yesterday at a local store and a used starlight express for cheap, can these be used to guide a scope?
How exactly is guiding achieved? I presume that I bright star is picked from a picture taken. does the program (like guide dog) then take controle of your scope?
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16" LightBridge
Nexstar 11" with CGE
Televue NP-101
Skywatcher short tube 4"
Nikon D70s
Canon 40D (modified)
"No Home for my scopes yet, but I have permission"
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c131frdave
Post Laureate
Reged: 01/17/05
Posts: 4376
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Quote:
My understanding of the DSI is that it can guide a scope but only if its a Meade. Since I have a celestron Im out of luck.
I don't think so. PM Shadowalker about it. He'll square you away (he uses a DSI and a non-Meade mount to guide). 
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Tak NJP
Various sizes and shapes of formed glass
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