DSLR imaging.

[simon84]

Morning all,

I want to start taking some astro pictures which I have zero experience at doing. I've three options available to me and would love some feedback on each with regards to the best way to start out.

First option, using my dslr on my Explorer 300P by way of a t-ring and 2" adapter.

Second option, piggy back my DSLR on the 300P and use my 75-300mm telephoto lens.

Third option, invest in 66mm, 72mm or 80mm ED Apo.

Will going the third route really provide me with much more than using my 300mm telelphoto lens?

The first option is probably the simplest at the moment but I did have some problems with my 300P being slightly too long and not being able to achieve focus, this was reported by the S@N magazine when they reviewed the scope back in 2008 and I have the one that they reviewed which takes me onto options 2 and 3 but before investing in an ED Apo I'd like to hear that there are deffinite advantages to doing so.

Apologies if my question has an obvious answer, but I would really value hearing from experienced imagers on this.

[themos]

Until an experienced imager comes along, I'll say start with the camera lens and learn the tricks. That's what I'm doing, slowly. Then move into APO wide-fields and finally on to the long-focal-length big apertures.

[jgs001]

I'd agree with that. In fact, I'd be tempted to remove the big newt, and mount the camera and lens directly on the NEQ6 with a dovetail. It'll make things simpler.

[michael.h.f.wilkinson]

I used a 400mm f/5.6 Apo telephoto from Sigma in the past (on film), and is a very well-corrected lens, with very little vignetting, so it is an excellent astrophotography lens. I have not compared it to an APO F/5 or F/6 from the likes of TMB or WO, but it may well be comparable. The 300mm end of a zoom is probably neither as fast nor as well corrected (especially regarding vignetting). A common piece of advice when using regular lenses is to stop them down a bit for astronomical work, which punnishes deviation of the point-spread function from the ideal towards the edge of the field mercilessly. This means you end up at F/8 or F/11 which does not compare well to a fast APO.

Piggy-back and prime-focus photography are very different propositions. The field of view at prime focus is 5x smaller (linearly, surface area 25x smaller) than that of a 300mm telephoto. Thus, piggy-back photography (like the use of fast APOs) is aimed at far more extended sources than prime-focus work.

[MishMich]

I've tried imaging through the telephoto, my ED80, and my f/6 8" SPX. Not a lot, because of the weather. But, I find that for large stuff, the Newt has trouble fitting it all in. Can just squeeze in the brightest of M42, and M45 is at the edges. Getting a good image and focus with a telephoto with adustable focal length was a problem for me. A fixed focal length lens is better, but apart from the 50mm, they aren't cheap. The image through my ED is much better than using a stock camera lens. I am sure one of the £500+ telephoto's would match it, but what is the point? The FOV is wide - M42 and Running man fit easily, as does the flame and horsehad, and Pleiades leaves plenty of room to pick up any nebulosity around them.

I agree with others though, start with the camera. The 50mm is a good lens, and will fit the whole Orion consetallation. Then look at an ED. The problem I found was I went straight into using the ED & SPX. When I started, the best I could manage with the ED was a maximum of 30 second exposures. With a good alignment, I can push that to 3 minutes, but I do lose frames, and its not always easy to spot the errors until afterwards. That means guiding becomes necessary, and that can cost as much as the ED itself. The advantage of the SPX is I can use shorter exposures, because of the wider aperture, which is necessary, because any tracking error is magnified, movement is magnified along with the image. I also prefer the wider FOV of the ED. I tend to just go for the ED, unless I have been looking at planets with the SPX, when I tend to continue with that. Once I have my guiding set up, I'll have the ED with the DSLR and the 5" Meade with the QHY5, and use the Meade to track and the ED 80 for deepsky, and try out the QHY5 through the 5" for planetary as well. That will free up the SPX, hopefully, and allow me to do everything I want to with the two refractors.

Sorry it is so long winded, as I said, not been doing this long - but I'd agree that with the DSLR & lens, you can take wider shots, so tracking is not so critical, with the Newt it will be moreso, and with a small ED, it will soon become an issue because of the lengths of exposure you will find you need to get further into the object. Personally, I think the refractor is best, and I love using it. I just wish I had an ED100, or ED120 even, (or an ED180 - but they cost £18,000).

I'd like to have another go with the DSLR & 50mm f2.8, but there's so little time I tend to just go for the ED 80. I am sure I would get better results now than when I tried it before. If you do use the DSLR and lens, it might be worth getting a CLS clip filter. I didn't, I got a 2". That restricts me from using the DSLR - because I can only filter light pollution when connected to the scope. I don't think the clip filter works with the stock lens, but it shoudl do with the 50mm. If I were starting again, I wouldn't bother with the 2" filter, I'd go straight for the clip, as that also protects the sensor.

M.

[jgs001]

The clip filter would work with the lens you are indicating, the 75-300 as you have it listed as an EF mount in your Sig... the clip filters, being in body sit in front of where the rear element of the EF-S lens mount ends up.

[simon84]

Thanks guys for all the quick responses, I have three lenses for my Canon, an 18-55mm, a 28-80mm and the 75-300mm.

I really like the idea of mounting the camera directly onto the mount, never considered doing it that way.

The next time I get a chance I'll try it like that and see how it goes and if I'm happy and enjoying what I get maybe go down the Apo route.

[jgs001]

A couple of things to watch...

set the lens to manual (if you have IS, turn it off), and worthwhile using a strip of tape of some sort, focus using liveview on a bright star (zoom in all the way), once focused to lock the focus in place.

If you have some camping mat, then you can make a dew shield for the lens out of it, it'll help.

[simon84]

Thanks again John for the advice. I'm drawing up the sizes for a Losmandy size dovetail with a 1/4" whitworth bolt through it now, which my brother will make for me.

Cant wait to give it a go.

[michael.h.f.wilkinson]

The 50mm (for APS-size sensors) or 85mm for 35mm full-frame is also great for really extended sources such as comets. I have a Carl Zeiss 1.4 85mm lens, and a collection of other, fast fixed-focal-length lenses (all second hand), which is brilliant for piggy-back work, but I did NOT buy these for astrophotography, where a slower lens can be compensated for by longer exposure. I bet you can get nice shots with the stuff you have, provided you stop down a bit, and take slightly longer exposures. As others have said, tracking is not that critical. If you can get a second hand short telephoto (e.g. 135 F/2.8) which will fit your camera you should grab it.

Note that there exist adapters to fit older lenses to the new Canon mounts, which allow you to fit, e.g., my Contax/Yashica mount lenses to Canon DSLRs. These old manual lenses can be snapped up for very little money. The "disadvantage" of these adapters is that you lose automatic focus and aperture control (as if we need them)

I bought these fast lenses for theatre and ballet photography, where it is less customary take long exposure shots or ask the subject to freeze for a second or two

[simon84]

Thanks again for all the advice on shooting with my DSLR, I've got the laptop setup to control the camera using Canon EOS Utility but does anyone know if I can use live view actually on the laptop?

[simon84]

Not to worry. Just figured it out.

[themos]

You can record the LiveView stream as well:

EOS Camera Movie Record | Get EOS Camera Movie Record at SourceForge.net

[simon84]

Thats handy, is the frame rate good enough to then use the recorded stream in Registax?

[themos]

It maxes out at 25 fps, I think.

[simon84]

I'll have to have a play around with that later. Thanks for the link.

[jgs001]

Just something to watch out for, if you're using liveview when shooting. I've heard reports that you get amp glow on long exposures. This isn't a problem when not using liveview for shooting, as the 450d and 1000d have an auto amp off for long exposures

[simon84]

Ok cheers John, I'll check that out.

[MishMich]

I've used it on Mars, Jupiter and Saturn, and it has given me the best images I have managed - but up to recently, I have been limited to an Opticstar PL-130C, a CMOS webcam and a CCTV CCD camera to HDD. The result is higher definition than VGA, and probably on a par with an HD webcam. You need to set the live view output to x5 magnification, which can be done either on camera or through the utility. If you want to have a try at planetary imaging, it is certainly worth a try, if you are happy downloading Russian software hack for the EOS - it is released under the GNU licence, which tends to give me some confidence that it is not dodgy.

Do ask if you have questions about using it.

M.

[simon84]

Hello M, so is that possible using the dslr? If so, very interested to learn more about and where to get the software hack.

[MishMich]

You can get it from SourceForge:

EOS Camera Movie Record | Get EOS Camera Movie Record at SourceForge.net

M.

[simon84]

Well I've gone away and got myself a dovetail made that will allow me to mount my dslr straight onto my NEQ6 and as soon as the skies are clear I'll have a bash at getting some images.

I think for further down the road I'll have a look at investing in a Megrez 72mm and maybe a guidescope aswell, the ST80 looks like a popular choice.

Thanks all again for your advice and hopefully I can bring some images to the forum soon.

[Sam]

There's some great advice with using camera and a suitable lens but I think it also worth still trying with the 300p. If it won't go into focus then a low profile focuser may help, and/or moving the mirror up the tube a cm or two - sometimes this can be done by collimating the mirror up a bit. A well aligned scope should allow for exposures of up to 120secs and there's been some fantastic images posted of unguided images. The 300mm of aperture will allow for the reduced exposure times and I think you'll have some brilliant results on targets such as M51, M101, M13, M15 etc as well as M42.

Starting out with unguided images will make you spend more time on the alignment which is very handy for later on when you get into guiding.

Sam

[simon84]

Hi Sam,

I tried my camera in the 300P and was able to achieve focus and got some lunar shots this afternoon, posted my first one in the Lunar Imaging forum. I've learned a heck of alot tonight from just trying things out.

Unfortunatley I couldnt get the camera to focus when using my 2x barlow. Are there any EP's that will allow me to connect my camera to so that I can increase magnification?

Cheers,

Simon.

[room16]

Hope you don't mind me dropping in on this thread. I've been having a good read as i have also just purchased a 1000d and would like to learn more about the options for widefield astro and imaging through my 10" skywatcher.

Unfortunately for me i've had to go the low profile option on the focuser but luckily i found one relatively new and cheap, so hopefully that will be sat on there next week to test her out.

I've tried moving the mirror up, not good unfortunately, not enough length on the bolts and im also concerned about adding coma and such to the image. So that getting wound back down and recollimated as soon as i get 2 mins.