Long exposures with single arm fork...

[Alan Ciech]

Has anyone tried long exposure photography with a single arm fork mount? Celestrons se series has good features at a reasonable price. But i'm not sure how stable the one armed bandit would be with long exposures, especially under higher magnifications...

[dannat (Daniel)]

I have found the alignment with my 4gt a pain, and after takng iff the scope to mount a refractor on I don't think the side arm is the best way to hold a scope for photos - although it is probable someone has had better success than me

[[1ponders] (Paul)]

Unless there is someway for you to mount your scope on a wedge, then you won't have a great deal of success trying to image long exposure with a fork mounted (alt/az) scope.

[Alan Ciech]

Of course a wedge is needed and alighnment isn't a problem. I'm just a bit dubious of the stability from the single arm. They save a lot of weight with this design, and less weight equals less stability. I would hate to but it and then realise that the lovely go-to mount is useless for deep sky imaging.

[Matty P (Matt)]

Hi Alan,

I own a Celestron 8SE and have tried some long exposures with it. The mount can handle very short exposures say up to around 20-40 seconds without showing to much "Drift" or field rotation. The one fork in arm in Alt-Azmode is ideal for visual and planetary imaging but is definitely not stable enough deep sky imaging. If I were you I would be looking to invest in a good GEM.

Here are some DSO images I have taken with the SE mount with my DMK.

http://www.iceinspace.com.au/forum/s...ad.php?t=28106

http://www.iceinspace.com.au/forum/s...ad.php?t=27988

http://www.iceinspace.com.au/forum/s...ad.php?t=27885

Hope this helps

[Zuts]

Originally Posted by Alan Ciech

Of course a wedge is needed and alighnment isn't a problem. I'm just a bit dubious of the stability from the single arm. They save a lot of weight with this design, and less weight equals less stability. I would hate to but it and then realise that the lovely go-to mount is useless for deep sky imaging.

I dont think it will be useless. Assuming it is on a wedge then you should get some photo's as long as it can be guided. If it cant be guided then forget it as at that focal length any errors in Polar alignment and PE will show up after a minute.

However, I dont think it is really designed for DSO astro photography though may be OK for planets. At the end of the day if you get into astro photography then you will not be happy and will upgrade to a more stable setup.

As a visual scope it would be great, for learning about imaging then maybe more difficult as most beginners start imaging with wide field and not F10 sct's and after they gain some experience move on from there.

Paul

[Alan Ciech]

Cheers Zuts, thats good advice. They can be used with a auto-guider, and the're GPS compatible.

Nice one Matt. Have you got a wedge for it? You can get pretty precise alignment from google earth without the GPS software... Have you tried the f6.3 focal reducer on it? That would give lower magnifications, wider field of view and shorter exposure times too... I will probably end up buying the 8se too. They should be ok for long exposures if well aligned... I hope, or will end up putting it on a good GEM for deep sky imaging.

Thanks...

[Zuts]

Originally Posted by Alan Ciech

Cheers Zuts, thats good advice. They can be used with a auto-guider, and the're GPS compatible.

Nice one Matt. Have you got a wedge for it? You can get pretty precise alignment from google earth without the GPS software... Have you tried the f6.3 focal reducer on it? That would give lower magnifications, wider field of view and shorter exposure times too... I will probably end up buying the 8se too. They should be ok for long exposures if well aligned... I hope, or will end up putting it on a good GEM for deep sky imaging.

Thanks...

Hi Alan,

The GPS/Google Earth is great for a rough alignment for visual use but you will still have to drift align for photography. The focal reducer will help but you will still be at a FL of 1200 which is not exactly short. A wide field scope is around 600 FL and people still use a reducer on this.

Anyway, as i said you will definately get some photos out of it with guiding. Also I like the 8SE because the OTA can be removed. Then as you say you can wack it on a GEM. Also even better you will still have a easy to use goto alt/az mount and can use it for any other scopes you may purchase for visual.

Paul

[Matty P (Matt)]

Originally Posted by Alan Ciech

Cheers Zuts, thats good advice. They can be used with a auto-guider, and the're GPS compatible.

Nice one Matt. Have you got a wedge for it? You can get pretty precise alignment from google earth without the GPS software... Have you tried the f6.3 focal reducer on it? That would give lower magnifications, wider field of view and shorter exposure times too... I will probably end up buying the 8se too. They should be ok for long exposures if well aligned... I hope, or will end up putting it on a good GEM for deep sky imaging.

Thanks...

Hi Alan,

My 8SE is pretty much the same as it was from out of the box. I was contemplating on buying a wedge for it but after a bit of research, I found that the one fork arm is not stable enough for a wedge. Although there is a wedge for the 8SE, I think you would be better off buying a good GEM. I know of some people that have used a wedge on a similar Celestron scope and found it to put strain on the motors etc...

To get a precise alignment all you will need is your exact coordinates and a bright star. I got my exact coordiantes from Google Earth and with my GPS phone. If you aligned the scope well, the GOTO will be accurate and you should have no problems finding objects. On the other hand, Tracking in Alt-Az limits you to fairly short exposures otherwise field rotation will become evident.

I am currently in the process of buying a new mount. I will be using the 8SE OTA and a guidescope that will be piggybacked. Also I am on the look out for a f6.3 FR for a wider FOV.

Hope this helps and keep asking questions.