Any help greatly received

Got a beginners' question? No matter how elementary, our friendly forum community and magazine writers will answer it.

Any help greatly received

Postby Starbug121 » Tue May 17, 2016 5:40 pm

I am new to astrophotography and need some guidance. I have a celestron nexstar 130SLT along with a cannon EOS 1200D camera. Any tips on getting the best images for planets, nebula and the moon. I just got a remote shutter button to stop the shakes. I am looking for exposure times and the like. Please bear in mind I am a newbie so be gentle with me. I have got some good moon pics so far but now want to reach out further. Thank you in advance for any advice you can put my way.

Troy (starbug121)
Starbug121
 
Posts: 4
Joined: Tue May 17, 2016 5:14 pm

Re: Any help greatly received

Postby Gfamily2 » Tue May 17, 2016 7:49 pm

Hi and welcome.

The bad news is that because the SLT has an Alt Az mount rather than an equatorial mount, you're going to be somewhat limited in what you can image with your scope (explanation follows*).

Diffuse faint nebulae will probably be a challenge (or rather, something you save for your next mount), but the good news is that you should be good for imaging things like the brighter open and globular clusters, the Orion nebula and things like that.

For your lunar imaging, how are you using the dSLR? Are you mounting the camera using a t-adapter onto the focuser directly, or are you just photographing down the eyepiece? A little knowledge of what you're currently doing will probably help us help you.


*The problem with using an Alt Az mount is that it basically moves stepwise across the sky, so with long exposures, the field of view rotates - and this affects even relatively short images, so you'll be pushed to get good pin-point sharp images with anything longer than a minute or even less - hence the limitation for imaging objects that have a reasonable surface brightness. However, you can improve the signal/noise ratio by taking multiple images - each of about 30s and stacking them. Overall there will be some rotation between the first and last images, but software can de-rotate them.

If you want to image other planets, you might want to consider using a webcam - the planets are generally bright enough that you can capture a video of them, and use the individual frames for stacking.

Do you have a local astro society that you can join? - there should be people there who can help you more directly by showing you how to get the most from your equipment.
Scopes: Meade 8" SCT, Skywatcher 127mm Mak, Raffle winner of SW ST80
For imaging: Pentax K5, Asda webcam, Star Adventurer (new toy)
For companionship: Mid Cheshire Astronomical Group.
(Not a moderator)
Gfamily2
 
Posts: 452
Joined: Thu Jun 25, 2015 10:38 pm

Re: Any help greatly received

Postby Aratus » Tue May 17, 2016 9:19 pm

Hello!

All those objects you mentioned will require different settings, and techniques. I would start with the moon as it is the brightest and largest object, and focusing is relatively easy. A single shot can give a pleasing result. Since you are tracking a bright object exposure isn't an issue so use a low ISO setting, say 100 or 200. You then need to experiment with the exposure setting. Try not to go below 1/60th sec. On a Canon you can use the TV setting.

If you want to be more adventurous you could use the EOS software that Canon produce to enable remote operation of the camera.
I use EOS Backyard which you can trial or buy here
https://www.otelescope.com/index.php?/home/
I use an 11" Celestron SCT (CPC 1100) on an equatorial wedge, housed in a 2.2m Pulsar observatory. I use a ZWO ASI1600MC and Canon 500D for imaging.
Aratus
 
Posts: 807
Joined: Tue Jan 12, 2016 2:17 pm
Location: East Lincolnshire

Re: Any help greatly received

Postby Starbug121 » Wed May 18, 2016 2:30 pm

Thank you both for your insight, and I use a T ring adapted with the T ring Barlow lens if that helps. I am just getting to understand the functions of the camera and getting some pretty clear pictures of the moon. I also just downloaded the star stacker program to layer images. Now saying all of that is there any further tips? Any help is good help for me being a total newbie.
Starbug121
 
Posts: 4
Joined: Tue May 17, 2016 5:14 pm

Re: Any help greatly received

Postby Aratus » Wed May 18, 2016 5:19 pm

It is good idea not to use a barlow initially. It gives a narrow field of view, a dimmer image and shows up bad seeing. These are all things you can do without when you are learning! Once you can get good photos without a barlow, then you are ready to try with one.

Use the 'Tv' settings for single shots. The 'bulb' setting is best when remotely controlling the camera with software. Spend a long time getting the focus right.
I use an 11" Celestron SCT (CPC 1100) on an equatorial wedge, housed in a 2.2m Pulsar observatory. I use a ZWO ASI1600MC and Canon 500D for imaging.
Aratus
 
Posts: 807
Joined: Tue Jan 12, 2016 2:17 pm
Location: East Lincolnshire

Re: Any help greatly received

Postby Gfamily2 » Wed May 18, 2016 6:49 pm

Aratus wrote:It is good idea not to use a barlow initially.

On the other hand, you may find that you can't get focus without the barlow - which is not an uncommon problem for Newtonians.

The reason is that in a Newtonian the optical path is optimised to keep the secondary as small as possible, which means that the primary image is produced some way down the focuser. Fine for use with an eyepiece, but with the depth of the dSLR, you sometimes can't get that primary image positioned on the camera sensor no matter how far you rack the focuser in.

If you can't get a focus without the barlow, you may want to consider getting a low profile focuser - but that's an extra expense and it's not an ideal scope for imaging anyway.

As for general advice, focusing is critical and can be much helped by using one of several designs of focusing masks. The simplest is probably the Hartmann mask, the most commonly used is the Bahtinov mask, but I have heard the Carey mask recommended over the Bahtinov mask.

Comparisons here

You can fairly simply create your own Bahtinov mask - there's a generator here
I saved the template as a PDF, then printed it out, cut out the circle then laminated it. Cut out the slots, and attach it with duct-tape.
Attach the camera and the mask, move to a nearby bright star and focus until the spikes are symmetric. Take trial images to confirm using the camera's preview screen, then lock down the focuser (if you can) and remove the mask
Scopes: Meade 8" SCT, Skywatcher 127mm Mak, Raffle winner of SW ST80
For imaging: Pentax K5, Asda webcam, Star Adventurer (new toy)
For companionship: Mid Cheshire Astronomical Group.
(Not a moderator)
Gfamily2
 
Posts: 452
Joined: Thu Jun 25, 2015 10:38 pm

Re: Any help greatly received

Postby Starbug121 » Wed May 18, 2016 8:21 pm

Once again thank you both, I will try both of your suggestions and use the standard lens as apposed to the Barlow lens and see how that pans out for me. I will also give that handmade mask a try. I am all for trying anything and see what works best for me. If the clouds break tonight I will give it a try without the Barlow lens with a quick shutter speed. And I need to get some ink to print out the mask. As soon as I get some clear sky opportunity I will let you guys know how it panned out. You two are very helpful and I very much appreciate the help.

Troy
Starbug121
 
Posts: 4
Joined: Tue May 17, 2016 5:14 pm

Re: Any help greatly received

Postby Aratus » Wed May 18, 2016 10:32 pm

Gfamily2 wrote:On the other hand, you may find that you can't get focus without the barlow - which is not an uncommon problem for Newtonians.


Well, let's see if that is a problem here first before we worry the OP too much! :D You are right of course, and if that is the case then one of the solutions you suggest will certainly be worth looking at. (Personally I never had such a problem with a Newtonian, but I haven't used a Newtonian for 12 years - it may be a bigger problem with more modern models!) Otherwise I think barlows add extra problems that beginners can well do without. Having said that I have occasionally got fantastic photos with a barlow in good seeing conditions. :) Then again I have wasted whole evenings using one. :(

I have a Bahtinov mask, and I can also recommend them for visual and photographic work. The EOS backyard software has a numeric focus read out which ensures best focus everytime. I tend to use that for photographs now. Either way a good focus is the key.

Starbug121 wrote: You two are very helpful and I very much appreciate the help.

Two heads are better than one! :geek: :geek:
I use an 11" Celestron SCT (CPC 1100) on an equatorial wedge, housed in a 2.2m Pulsar observatory. I use a ZWO ASI1600MC and Canon 500D for imaging.
Aratus
 
Posts: 807
Joined: Tue Jan 12, 2016 2:17 pm
Location: East Lincolnshire

Re: Any help greatly received

Postby dave.b » Fri May 20, 2016 7:33 pm

My first 'scope was the 102SLT. To get my DSLR on the back off it I had to mount the tube on tube rings so I could reposition it on the mount to get it balanced. Without doing that you are in danger of the clutch slipping and putting a lot of strain on a low cost gear train.

A webcam or smart phone would be better.
dave.b
 
Posts: 797
Joined: Mon Feb 13, 2012 6:35 pm
Location: Staffordshire

Re: Any help greatly received

Postby Aratus » Fri May 20, 2016 7:41 pm

Good point, I hadn't thought of that. Another advantage with using a web cam is that being thinner, it is much easier to get its CCD at the focus point - in the event of that being a problem, of course!
I use an 11" Celestron SCT (CPC 1100) on an equatorial wedge, housed in a 2.2m Pulsar observatory. I use a ZWO ASI1600MC and Canon 500D for imaging.
Aratus
 
Posts: 807
Joined: Tue Jan 12, 2016 2:17 pm
Location: East Lincolnshire

Next

Return to Ask a silly (astronomy) question

Who is online

Users browsing this forum: No registered users and 0 guests