DSO imaging without a mount

[Owen]

A bit of background - I've been observing with my Skywatcher ED80 for a few weeks now with great success. Despite not owning a proper mount (I use a standard pan and tilt photography tripod as I bought the scope principally for bird photography) it hasn't been too difficult to observe some of the easier messier objects - M2 in the evenings, M42 in the mornings for example (my window faces South). I've been pretty blown away by the results already and I know the advice would be to keep learning my way around the sky and take my time getting into imaging, but as I arrived here very much from the photography angle I'm itching to have a go.

I won't be able to afford an equatorial mount for at least a year probably, let alone filters - even £200 is too much with other pressing concerns, so I'm trying to gage what, if anything, I might be able to achieve in the meantime. I don't need high quality images, they can wait for the requisite equipment and experience. Indeed if it's anything like birding, which I suspect it is, it will take a long time to feel even vaguely competent. But a bit of blurred colour from a nebula or galaxy on my LCD would be a great stop gap.

My plan for the near future is to find an 'easy' DSO - probably Orion as a starting point - and take a series of shortish exposures to avoid streaking, say 15 seconds each, totalling about 30 minutes. As my understanding goes the object will rotate through the series as the earth spins on its axis during that 30 minutes (or more likely several hours as I readjust the framing after each exposure). I'll then figure out how to stitch them together in GIMP (any links to tutorials for this progam would be much appreciated), which will probably involve cropping and rotating to realign them.

So - can this possibly work and what am I missing/doing wrong?

Cheers,

Owen

[SteveL]

Just load them all into DeepSkyStacker, and it will do all the alignment, rotation and stacking for you.

[Owen]

Just load them all into DeepSkyStacker, and it will do all the alignment, rotation and stacking for you.

That's what I like to hear

[rocketandroll]

Hi Owen

You will be limited without a tracking mount... but it's not impossible.

Through the ED80 you should be able to get 10 - 15 second subs without too much star-trailing, you may just have to do a few tests to see what is the longest you can get away with.

A T-adaptor to attach your DSLR to the scope won't cost too much, £20 - 30 max for the bits you'll need.

Aim for a pretty high ISO, 1600 I guess if you can do it, maybe 3200 if you dare :-)

As you say, take a good 30 or 40 shots (you may need to manually re-point the scope to re-frame the target every few shots) the more you get the better the finished result will be.

Download a copy of Deep Sky Stacker... it's a free piece of software that is very easy to use. Load in all your sub frames, set it stacking... ten minutes or so later, you'll have a nice stacked image of all the exposures...

You will then want to have aplay with it in some image edditing software such as Photoshop (if you have it) or Gimp which is a free alternative... a simple 'levels stretch' will bring out lots more detail.

There are lots of tutorials around on image processing, or ask the folks on here and someone will help you out.

I'd agree.... M42 is a good target... you can get quite a lot of detail from it even in 10 seconds or so at a high enough ISO. Some of the brighter globular clusters might also be viable with 10 second subs. M31 might be worth a stab, it's certainly the only galaxy you are likely to have much luck with... if you were going to do that i'd suggest doing it with a camera lens not a scope... at about 200mm it fits in nicely and camera lenses will generally go to a larger aperture (f4 at least normally) than the f7.5 of the ED80 so you can catch at least four times as much light in the same time.

Hope that helps, and good luck!

Ben

[Owen]

I'd agree.... M42 is a good target... you can get quite a lot of detail from it even in 10 seconds or so at a high enough ISO. Some of the brighter globular clusters might also be viable with 10 second subs. M31 might be worth a stab, it's certainly the only galaxy you are likely to have much luck with... if you were going to do that i'd suggest doing it with a camera lens not a scope... at about 200mm it fits in nicely and camera lenses will generally go to a larger aperture (f4 at least normally) than the f7.5 of the ED80 so you can catch at least four times as much light in the same time.

Hope that helps, and good luck!

Ben

It certainly does help thank you. A quick question though, surely Andromeda would just be a tiny smudge in the image at 200mm or am I missing something? I have a decent 200/2.8 which would do a great job optically, I just assumed the focal length was too short to get anything meaningful.

[Owen]

Oh and one more question!

Would you recommend using the in camera long exposure noise reduction in which case it will be a long night or to do this in GIMP afterwards?

Thanks for you patience

[Stephen]

Barn door / scotch mount? Costs less than a night out to make one and increases your exposure length a lot

[stan26]

Before I got my telescope/mount I tried to Image the M42 orion neb using just a camera tripod with my 500D and 300mm lens. I found that even subs as short as 10sec would show star trailing at 300mm. My advise would be, wack your ISO up to say 3200 or even higher! I probably wouldn't use the iso noise reduction setting but thats purely because I have methods of reducing noise during the processing stages. Keep the subs to 5 sec's long, you'll be suprised how much you'll catch with such short subs, and take loads of them, A remote shutter release will help, especialy a timer version that you could let it take maybe 20-30 subs then move the target back into the centre then start again. Shoot in raw, take a few darks, load them all into deep sky stacker, then get the final stacked image into gimp and strrrrreeeetcchhhh that histogram! I think after some practice you'll get some pleasing results.

Here is one of my early attempts at the orion neb through my startravel 102. It's just a single 30sec exposure at ISO3200. I think 50+ 5sec exposures could look even better!

http://stargazerslounge.com/imaging-deep-sky/133932-first-dso-m42-re-edited.html

stan.

[dph1nm]

camera lenses will generally go to a larger aperture (f4 at least normally) than the f7.5 of the ED80 so you can catch at least four times as much light in the same time.

A 200mm lens at f4 is only 50mm aperture, so you have less light to play with overall.

NigelM

[michael.h.f.wilkinson]

A 200mm lens at f4 is only 50mm aperture, so you have less light to play with overall.

NigelM

Less light but more photons per pixel, which is what count more in extended sources. One of my best shots of a comet was an (unguided) 12 min exposure with a 85mm F/1.4 stopped down to F/2.0 using 100 ISO slide film. The camera was put piggyback on the GP-C8 mount. I had to use 100 ISO because that was what was in the camera, but the massive speed of the lens made it work. For extended sources focal ratio beats focal length.

[rocketandroll]

Yeah, sorry, should have clarified that, obviously a camera lens with a smaller primary will catch less photons, but they have a much shorter focal length than a scope so, typically, yes, you get more photons per pixel :-)

As for M31 fitting in a 200mm lens.... it's HUGE... here's my pic of it through a Canon L series 200mm f2.8 lens:

I should add, that was with about an hour and a bit of 2 minute subs at f2.8 and ISO800

Not sure what you'd get with 10 second exposures?

Ben

[Owen]

Yeah, sorry, should have clarified that, obviously a camera lens with a smaller primary will catch less photons, but they have a much shorter focal length than a scope so, typically, yes, you get more photons per pixel :-)

As for M31 fitting in a 200mm lens.... it's HUGE... here's my pic of it through a Canon L series 200mm f2.8 lens:

I should add, that was with about an hour and a bit of 2 minute subs at f2.8 and ISO800

Not sure what you'd get with 10 second exposures?

Ben

Well not a lot as it turns out! I had a go at the weekend at a site in Mid-Wales. Very dark - the Milky Way is clearly visible even with the moon almost full. Andromeda was a fuzzy speck even with the 80ED on my LCD after 5-15 second exposures, ISO 800 - 3200. My guess is that what I'm seeing is just the core of the galaxy and that actually, it's much bigger. I'll compare its extent in relation to other stars in the images and cross check it with your image to confirm.

It may be the rest of it will start to appear if I start stacking images but I only took 30 5 second subs as the cloud rolled in. Without a tracking mount the stars streaked even in 5 second exposures. There was also some movement in the tripod as it's just not designed for this kind of photography.

Still I got some red and green out of Orion, it's a start! I'll upload some example shots when I get home and you'll see what I mean. I think the proper mount and tripod will have to sneak themselves into the budget sooner rather than later.

Still with such good skies there was some excellent observing. Jupiter as always was a crowd pleaser. Even my 3 year old niece was impressed!

[carastro]

Personally I wouldn't have thought you could do long exposures at all with a telescope and no tracking mount and as you have found out you will not pick up any nebulosity without long exposure. Shame really as you've got the enthusiasm but not the right equipment.

You could probably do better just using the camera lens and do widefield as you could then get away with exposures of up to 30secs maybe until such time as you can get a an EQ mount. I would recommend an HEQ5 or NEQ6 depending on the size of scope you want to put on it.

Doing this will give you good practice for later, as you will be familiar with the settings and stacking procedures.

When doing long exposures it is normally recommended that you turn off the auto noise reduction in the camera as this means say each 5minute exposure will take 10 minutes, and it is better to do the "darks" when the clouds roll in and not waste precious clear skies, however if you are doing wide field and short exposures it would not make a lot of difference.

Hope this helps.

Oh, and as some-one suggested above there is a Barn Door method, which I know nothing about, but it appears to be cheap and works, might be a good idea to look into that while you are waiting.

Carole