Astro Photography

[Mr.A]

Hullo,

As soon as this never ending rain cloud passes i'm planning to take my new newtonian out to play. I've purchased an adaptor for my DSLR body to fit the barlow eyepiece, so I think i'm set to go as soon as the skies clear.

I've been enjoying photography for a lot longer than i've started investing in astronomy, so i've got the patience to trial and error until I get what I want, but are there any suggestions you might have to help me get things right sooner rather than later?

I have a Skywatcher 130P on an Alt-az mount (the go to one) so i'm dubious about the tracking. I'm thinking that the moon won't require long exposures, certainly not longer than 1/125?

With Deep Sky objects I'm thinking the zig zag tracking will ruin longer exposures, though i've heard a program called Registacks (?) will sort multiple exposures to create a detailed image?

As you can see, I'm flailing in the dark! Any help would be good - don't hesitate to be blunt with me if i've been speaking waffle!!

Thanks in advance

Mr.A

[pvaz]

I know nothing about astro photography, except what I read. But since there are no replies yet here are some thoughts:

The 1st thing you need to do is find out if you can reach focus with that camera on that scope. Some scopes come ready for visual and the focuser doesn't have enough travel (in or out) to reach focus on a DSLR. Out travel is solved easily with an extender, in travel may require you to mod the focuser or replace it.

After checking that, start with the moon and work out from there. Wait for others to advise cause I'm a bit out of my environment here...

[Mr.A]

Thanks for the response - lots to consider that I hadn't thought of already!

[barkis]

Hello Mr A.

Pvas is quite right concerning the telescopes focal plane reaching the sensor of your camera. If when you insert your Barlow and camera into the focuser, and rack the focuser in and out using its maximum travel, somewhere in that travel, you may get a sharp focus on the moon. You can even try on a terrestrial target, but choose one that is at as great a distance as you can.

If you can get a sharp focus that way, and the target is far distant, make a note of the focusers position, then begin to turn the focus knob slowly in the direction that moves the camera towards the scope tube. If there is say a further .5" of movement, then I would say you should be able to target the moon and get some Images. Being a photographer, you know how important good focus is. Also, you must use manual settings when doing astro stuff.

Auto exposure won't do a good job on the moon, you need to experiment with times, taking into account the phase of the moon, the fuller it is, the shorter the exposure, and vice versa.

Iso can be 100 200 even 400.

The best way is to bracket exposures, Start short, say 1/250th, then two or three at slower speeds. You will soon derive the correct exposures for different phase conditions.

The moon is a great target for the camera, and I'm sure you will enjoy good results in no time at all.

Good Luck.

Ron.

[Mr.A]

That's really useful, I was concerned by the ISO/Noise trade off, I think experimentation is the way forwards.

Thanks for your advice Ron, nice REME cap badge too!

Thanks

Andy

[barkis]

That's really useful, I was concerned by the ISO/Noise trade off, I think experimentation is the way forwards.

Thanks for your advice Ron, nice REME cap badge too!

Thanks

Andy

Thanks Andy. Yeah!, very happy years. I'd like to do it all again.

Ron.

[Mr.A]

When I was younger and considering joining the Army, it was the REME I was thinking of, I even remember Arte et Marte (Sp?) seeming awfully profound at the time!

[Cornelius Varley]

With Deep Sky objects I'm thinking the zig zag tracking will ruin longer exposures, though i've heard a program called Registacks (?) will sort multiple exposures to create a detailed image?

If you are intending to photograph DSOs your mount will not be suitable. As you have already mentioned the zig-zag motion of an alt-az mount will cause a similar affect to the images taken. In imaging DSOs the mount is the most important part of the imaging setup. The mount needs to be able to accurately and smoothly track across the sky following the stars. An equatorial mount usually equipped with an autoguider port is recommended. A second, smaller telescope is attached to the mount and a guide camera attached to this telescope, this camera sends images back to the laptop where software analises the images and sends control signals back to the mount to correct drifting. Processing software (Deep Sky Stacker or similar) is used to process the images taken by the main camera.

Registax or Avistacker are normally used for lunar and planetary imaging, converting avi clips taken by webcams, stacking ithe individual frames of the video clip to improve the signal to noise ratio.

As others have already mentioned, there sometimes is a problem using this telescope and a DSLR at prime focus. That is to say that the telescope has insufficient inward focusser travel. The telescope now features a 2" focusser so this may help.

Peter

[jazzmeister]

If you can afford it go for a decent equatorial driven mount. I use a EQ6 Pro and it is fantastic, I also use a Meade LXD75 10" Scmidt Newtonian for my scope (forget the Meade mount however) the EQ6 Pro is rock steady even with my large scope, perfect for long exposures.

[jgs001]

If you can get your SLR to focus at prime on that scope (I've heard there's not enough in travel, and that would involve modding the scope, and shifting the mirror up the tube). Then whilst the mount isn't ideal for Deep Sky, it will work. You just have to work out the limitations, go up to them and shoot shedloads of exposures. Imaging a target low in the east or west will allow for longer sub lengths (I managed 2 minute exposures on M31 on a NexStar SLT), but as the target gets further North or South, or overhead, the shorter the sub lengths go. Having said that, if you get enough subs, you can still pull out Ha nebula (Infrared) on an unmodded camera, ok it took some 150 subs of 40 seconds each... .

As you say you're a keen photographer, I would expect you have a nice selection of lenses. What you could do, is to invest in a dovetail, mount your camera with a lens fitted to it, and capture some wonderful widefield images with it mounted on that little AltAz mount. (400mm is about the right focal length to easily fit the Andromeda galaxy on the chip), and the shorter the focal length, the less susceptible to mount tracking errors.

I can post some examples if you like of images I took with my NexStar SLT and a 400mm ST80 clone.

Don't get me wrong, a decent EQ mount will make life so much easier and less frustrating, but you can use what you have and get decent results out of it.

[dph1nm]

I agree - you can image most of the Messier objects on an Alt-Az mount without any problem. Even with subexposures as short as 16sec.

NigelM