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pixueto

10 min subs with budget setup. Is this alright?

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Dear all,

On Saturday I went out to run some tests with my budget guiding system (EQ5 with the shoestring mod) and this time I tried 5 mins and 10 mins subs from my garden in SE London. I wanted to see if I could really do 10 mins subs from my light polluted corner. I'd really welcome your comments on this one. I'm not particularly impressed with the quality of the picture but I managed to get 1hour, 50 mins worth of those 5min/10mins subs, ISO 800 and no LP filter. I only discarded a couple of them because of satellite trails. Is this it? Could I now, in principle, go about imaging this galaxy for a few hours with those long exposures to improve the picture? Or am I missing something here and there is something terribly wrong with que tracking, LP, etc?

I'd really like your feedback on this one, as I'm just starting with guided imaging and I'm trying to determine which are the most suitable time exposures for the kit I have.

Thanks again for helping with your expertise :).

post-30999-133877774657_thumb.jpg

Edited by pixueto

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Pixueto,

did you take any Darks and flats to go with your Lums ? you didn't say mate.

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Yes, I did take both darks and flats. I didn't manage to remove the vignetting entirely though so I had to use Pixinsight.

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it looks really good but also shows be of coma, try added a baader MPCC to the optical train for a flatter image then fine tune from there. But other then that you are off to a good start.

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^^ as he said, a bit of coma, but a great image, had a little tweak at it but I'm learning myself :) I'm sure someone else could do better...

post-24384-133877774701_thumb.jpg

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it looks really good but also shows be of coma, try added a baader MPCC to the optical train for a flatter image then fine tune from there. But other then that you are off to a good start.

Thanks for your feedback. I really appreciate it.

So you think ISO 800 and 10min subs will work with my budget kit? I was concern about the noise (loads of LP in my area) and the quality of the tracking using a EQ5 but I also expected to get more colour and detail from those longer exposures; however those details and colour are nowhere to be seen in the picture -at least with 1h 50mins total exposure time!

Using a coma corrector, wouldn't it add a level of complexity to the imaging train? I'm thinking about longer time exposures needed, etc. That's why I'm a bit reluctant to adding other lenses to the kit. I always thought that I can crop the images as coma doesn't occur in the centre of the picture.

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^^ as he said, a bit of coma, but a great image, had a little tweak at it but I'm learning myself :) I'm sure someone else could do better...

Thank you, with your rework you added more colour and the dust bands can now be seen. On the other hand, there is slightly more noise. I suppose more darks and lights are needed.

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You've done well to get 10 min subs with a 200p on an EQ5. The details come out by stacking lots of subs, hopefully the signal would outweigh the noise. If you're struggling with LP on 10 min subs I would drop down to 5 mins. Post an un-processed sub of each exposure length and we can see the difference.

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Thanks for your feedback. I really appreciate it.

So you think ISO 800 and 10min subs will work with my budget kit? I was concern about the noise (loads of LP in my area) and the quality of the tracking using a EQ5 but I also expected to get more colour and detail from those longer exposures; however those details and colour are nowhere to be seen in the picture -at least with 1h 50mins total exposure time!

Using a coma corrector, wouldn't it add a level of complexity to the imaging train? I'm thinking about longer time exposures needed, etc. That's why I'm a bit reluctant to adding other lenses to the kit. I always thought that I can crop the images as coma doesn't occur in the centre of the picture.

No it won't add much, just space it out at recommended specs from the chip and your golden. The image will be much flatter and look a ton better w/o any light loss through extra glass. Cost is about $120 from most shops. Not to mention there are a ton of targets coming up where you want the entire FOV w/o cropping out the coma stars.

As far as the iso800, sure keep it at that with the 350d. When I was using my 1000D, I shot EVERYTHING in iso1600. How did I get around noise...well I made this for $15, weighs 3 extra lbs but is a life saver in the summer months and also when doing 5-10min subs. Also if you're worried about LP, invest in a filter, either clip in or 2". I'd vote 2" just in case you'd ever like to go pure CCD, the filters will transfer over. I'm in a orange/yellow zone, couldn't image more then 2mins w/o a LP filter or Ha filter.

This cooler doesn't look that great but gets the job done w/o opening the camera again. Without it, 5min @ iso1600 chip temps would rise from 80*F to 110*F by the end of the night. With this simple cooler, chip temps stay in the 55-60* range then entire night. Also allowing dark frames to be temp matched MUCH better and gets rid of the graininess on the final photo.

5767134620_8c730d25cd_n.jpg

Camera cooler_01 by jsigone, on Flickr

5766590865_2cb5384f94_n.jpg

Camera cooler_02 by jsigone, on Flickr

5767135342_b63288e72b_n.jpg

Camera cooler_03 by jsigone, on Flickr

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you've done very well with that setup, I'm sure many people would have said it can't be done with a 200p on an EQ5. Tracking looks great, just a bit of coma, easily fixed with a Baader coma corrector (which work fantastic by the way). Just take more and more subs. The 350d is actually very low noise, compared to the more recent Canons (low megapixel). ISO800 is more like ISO400 on the later cams.

Have you got a photo of your setup? It would be useful for others to see what can be done with that combination.

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You've done well to get 10 min subs with a 200p on an EQ5. The details come out by stacking lots of subs, hopefully the signal would outweigh the noise. If you're struggling with LP on 10 min subs I would drop down to 5 mins. Post an un-processed sub of each exposure length and we can see the difference.

Thanks for your feedback. There you go, a 5min and a 10 min sub as you requested.

post-30999-13387777473_thumb.jpg

post-30999-133877774737_thumb.jpg

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No it won't add much, just space it out at recommended specs from the chip and your golden. The image will be much flatter and look a ton better w/o any light loss through extra glass. Cost is about $120 from most shops. Not to mention there are a ton of targets coming up where you want the entire FOV w/o cropping out the coma stars.

As far as the iso800, sure keep it at that with the 350d. When I was using my 1000D, I shot EVERYTHING in iso1600. How did I get around noise...well I made this for $15, weighs 3 extra lbs but is a life saver in the summer months and also when doing 5-10min subs. Also if you're worried about LP, invest in a filter, either clip in or 2". I'd vote 2" just in case you'd ever like to go pure CCD, the filters will transfer over. I'm in a orange/yellow zone, couldn't image more then 2mins w/o a LP filter or Ha filter.

This cooler doesn't look that great but gets the job done w/o opening the camera again. Without it, 5min @ iso1600 chip temps would rise from 80*F to 110*F by the end of the night. With this simple cooler, chip temps stay in the 55-60* range then entire night. Also allowing dark frames to be temp matched MUCH better and gets rid of the graininess on the final photo.

5767134620_8c730d25cd_n.jpg

Camera cooler_01 by jsigone, on Flickr

5766590865_2cb5384f94_n.jpg

Camera cooler_02 by jsigone, on Flickr

5767135342_b63288e72b_n.jpg

Camera cooler_03 by jsigone, on Flickr

Thank you very much for sharing your expertise. It seems that a coma corrector in next thing on the list. Really clever setup you got there. My mount wouldn't take that extra weight though as I'm guiding with the finder.

Edited by pixueto

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Thanks for your feedback. There you go, a 5min and a 10 min sub as you requested.

ouch...+1 for lp filter!

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I would get a coma corrector and a 2" Astronomik CLS filter too.

The CLS will make a HUGE differnce.

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ouch...+1 for lp filter!

:) LP, Is it that bad? Oh dear:icon_confused:

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Woah that's pretty bad LP. Filter without a doubt. It makes the great story even more remarkable.

Edited by ianaiken

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Thank you very much for sharing your expertise. It seems that a coma corrector in next thing on the list. Really clever setup you got there. My mount wouldn't take that extra weight though as I'm guiding with the finder.

LOL I thought and was told the same thing, I have 25lbs on a mere celestron CG5 and get 10min subs if the wind is nice to me :) Its all about balance...

Try it, if it doesnt work at least the ice packs will keep your sodas cold:evil6:

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But look at it this way, your tracking looks great. :)

Everything else can be fixed more easily.

Defo. go for an LP filter and a corrector. But more importantly, more subs.

Cheers

Ian

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Have you got a photo of your setup? It would be useful for others to see what can be done with that combination.

Took some photos last Saturday but I can't find the phone lead to download it to the computer (i took them with the mobile phone). I'll post it when i find it.

Basically I use a SW200P with the modded port from shoestring. I use a stellavue finder which takes eyepieces + a 2X barlow to reach focus with a philips SPC 880 for guiding through PHD. Also a Canon 350D without any filters -as you know:)

Edited by pixueto

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Thank you, with your rework you added more colour and the dust bands can now be seen. On the other hand, there is slightly more noise. I suppose more darks and lights are needed.

It's harder working from the jpeg, you'd get better results from the tiff. All I did was a quick play with the curves.

If you do get a coma corrector, they are threaded for a 2" filter so you could try a cheap LP filter on there. The Baader MPCC will work with the standard camera T-ring, the skywatcher CC will need a different T-ring. The CC simply goes between your camera and the 'scope, no changes to exposure. Adding an LP filter may mean you need more subs but the difference is worth it... there is a quick before/after comparison here http://stargazerslounge.com/showthread.php?t=185148&highlight=light+pollution+comparison

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I reckon I'd try an LP filter and 5 min subs. I did a comparison using my skywatcher LP filter and without it a while back.

Just foind the pics again now :)

This is a 10 min sub of M31 without an LP filter.

picture.php?albumid=1911&pictureid=13676

and this is the addition of a skywatcher 2" LP filter taken directly after, same length sub 10 mins on M31.

picture.php?albumid=1911&pictureid=13677

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If that was 10mins unguided then that is incredible - your tracking is perfect! :headbang: And that's a very good image for first try :) Wish I could get my tracking as good :)

Oh, and yes, you want an LP filter. I think the Astrononik CLS is the best but quite expensive.

Edited by Gina

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Thank you all for your feedback. After your comments, I've been reading some other threads on LP filters and I'm a bit confused. Some people think there are not really that good and it may be better to go for shorter exposures with no filter at all. What do you think? I had once a baader nemodyum LP filter for visual and it didn't make much difference visually I have to say. what about lowering the ISO in the camera? By the way, should the histogram appear silghtly over the middle of the scale (as with flats) to get the best quality and avoid saturating the sensor? Should I modify the exposure/ISO/LP filters to achive this? Sorry if this is a dumb question!

On the other hand I'd love to push the mount to the limit with those longer exposures. It would be disappointing to end up doing 2 mins exposures after all this trouble to mod the mount, getting a finder with eyepieces, etc just to find out that i don't need guided images!

Edited by pixueto

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If that was 10mins unguided then that is incredible - your tracking is perfect! :headbang: And that's a very good image for first try :) Wish I could get my tracking as good :)

Oh, and yes, you want an LP filter. I think the Astrononik CLS is the best but quite expensive.

Oh no Gina, that was a guided one but with a budget setup: EQ5 + SW200P with the hand controller modded to send pulses to the mount via PHD.

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