15 replies to this topic

[Branimir]

After my first quick attempt to image a DSO and quite disappointed from the results I decided to post this question if possible to prevent trying to invent the wheel anew. 

First of all I am not going in a direction of dedicated astrophotography or anything like that. I got an 8" Dob for the purpose of showing some of the wonders of the Universe to my group of students (children and youth ages).

I was wishing that we will be able to make some photos as well of some prominent and "easy" objects as part of our astronomy projects. Well, having never done this before I had to prepare myself and do some successful tryouts beforehand since once under the stars with the children, time will be very limited. I'm not sure if I have unrealistic expectations.

 

The Equipment is:

* 8" GSO Old Dob

* Self made EQ-Platform

* Canon EOS 1100D (Rebel T3)

* Self made clamp to attach the camera (with it reaches focus without problem )

 

Look at this single shot of M13 with 8s exposure, ISO 6400, using prime-focus through 2x barlow  

Made from the backyard, the skies relatively clear (the Milky Way could be seen)

 

 

here is with contrast increased

 

 

Honestly I expected more from 8s on ISO-6400. 

 

So this are the issues I faced and will appreciate any input on it.

 

• Focusing - when I zoom a bright star 10x in LiveView with every touch of the focuser the view shakes so much that the star goes out of the screen.
• Pointing at the object (is it called framing?) - Since I have only a Telrad Finder I was hoping will be able to see my object on the screen but ... only black, even in the highest ISO. Through the eyepiece I could see the cluster very prominent. So I had to do some tryouts with exposure > 6s and readjust until I get it in view and bright enough to detect it on the camera screen.
•  Image not stable - very few of  the shots looked more or less steady, most were blurry. The EQ Platform seems to keep the image quite stable through the eyepiece so I wonder if it was not the result of the mirror slap (quite a loud one)
• Mirror Lock Up - found no way to trick it into it. Even in LiveView the mirror makes a slap at the end of the shot (cannot understand why). Installed MagicLanterns but no Mirror Lockup neither. See the following image. Since the trails are not straight makes me think that it is not the EQ-Platform's fault but rather shaking. Should I take a video instead (there the mirror stays up)?

 

What I am hoping is to be able to get a decent and sharp photo of some of the easiest and prominent Clusters, Galaxies, Nebula with the equipment already available in a simplest way. Not expecting any fancy or breath-taking results.

But maybe it is not realistic - I have no experience with this - only info I have found online. I am aware of stacking, black frames etc. + post-processing but wanted to solve the first issues before going there.

Im I doing something wrong?

[unimatrix0]

Few questions: 

 

1. Is your mount tracking?

2 Did you polar align the mount? 

3. You said it's a home made EQ platform? Does that mean motorized and have a go to function? 

4. Are you using an intervalometer with the camera, or at least some remote device the trigger the shutter on the camera?  

5. Judging from the images you shown, it's both tracking issue and shaking. 

 

How is this camera attached to the telescope?  Are you attaching it like sticking it into the diagonal?  

 

Also, loose the barlow! Also no diagonal!  

 

The reason your images are faint, because your barlow (I don't know if it's 2x or 3x you are using) essentially reduced the light gathering capability of your telescope by several steps. Your camera now is looking through a tiny hole of the barlow instead of the 2" or 1.25" diameter focuser. 

The diagonal also introduces another inefficiency by bouncing the light (again) and you just keep losing photons. 

 

You will need more extension pieces without the diagonal and the barlow, but you will have much brighter images. 

 

 

 

p.s. 

 

If you just want to shoot something easier, you won't even need a telescope. Just a tripod and a camera lens. 

 

Watch Niko here, this applies to any DSO out there, although aim for the brighter ones

https://youtu.be/pXc...cutoF3br2CTqiGa

Edited by unimatrix0, 08 August 2024 - 09:55 AM.

[idclimber]

Drop the Barlow. It will not help you even if you had a better mount.  All it is doing is restricting light. 

 

The only other piece of advice is to inform you that you are trying to climb Everest as a complete novice. Oh, and you are wearing jeans and a T-shirt. Getting an 8" Dob working well with a DSLR is extremely challenging to say the least. There are lots of things we can suggest, but most involve spending money and buying gear. 

[gsaramet]

What the guys said above. There might be a few things you can do to improve for no/little money.

 

Focus: print a bahtinov mask on cardboard. Much easier to focus than with the eyeball. Don't leave it on the scope

 

Shakes: you need to release the shutter remotely. Maybe you camera can be accessed via bluetooth? Else, a remote release or an intervalometer

 

Keep the optical train as simple as possible. If you can connect the camera to the focuser tube, it's a good idea. Using barlows or diagonals it's not. 

 

If you are not motorized, you need to find your longest safe exposure (it varies on the sky). Testing kinda works And then you'll stack or do EAA. 

[Tkall]

Maybe give the moon a try.

[KSPSteve]

Yeah, you might be expecting more than is possible with your setup, at least not without a lot of frustration and effort.

I know you said you're not going in the direction of astrophotography, but you might want to look more into EAA, Electronic Assisted Astronomy, which is just using a scope with a camera to show live images of space objects.

I do EAA all the time at star parties, and it truly blows people away, young and old, to be able to see things like the Andromeda Galaxy, Orion, Eagle Nebula, M13, etc, live!

Not sure if you have any budget available, but you could get started with EAA "relatively" inexpensive, maybe under $500?  (Not with the Dob!) Just thinking out loud.

Good luck.

-Steve

 

[Sheridan]

It does not look like your mount is a tracking mount. So at the focal length using a Barlow which by the way slows the system down considerably, your individual sub exposures would have to be much shorter than 8 seconds.  I would suggest dumping the Barlow unless you're shooting planets. The second suggestion would be try using sharp gap pro and do EAA.

[Spaceman 56]

Smiller is the man for advice about imaging with Dobsonians.

 

simple and achievable advice from me would be to experiment with exposure time, and see how long you can shoot without the stars blurring from movement.

 

once you have worked out the longest exposures which can be had (without tracking) back off the exposure time by a second or so and then

crank up the ISO until the image deteriorates.

 

thats about as good as you will do (without tracking) for a Single sub exposure.

 

please understand that if you learn stacking, you can take many (even thousands) of single sub exposures, and blend them together and get a much better image.

 

Good Luck. 

 

PS, as iDclimber says, dont use a Barlow

Edited by Spaceman 56, 08 August 2024 - 04:15 PM.

[Skysmacker]

Maybe you could use a 2 second timer before you take each shot. 

 

seems like that would help with the shaking. 

 

Not sure you need mirror lock up though. Unless it’s a short exposure thing or something using a DOB?

nice first attempt! I can see the cluster

Edited by Skysmacker, 08 August 2024 - 08:20 PM.

[Branimir]

I appreciate all your suggestions. It definitely gives me something to start with.

Just to answer the questions above:

- The EQ Platform is motorized. ToGo - no.

- I have a compass on it and 2 ways bubble level for proper alignment

- The posted photos were made with remote trigger on cable

- The camera it so happens that it just fits tight in the focuser and with a clamp I am supporting it very stable (the most stable part of the setup I'd say)

I noticed that the gear was slipping on the shaft so the tracking was not accurate from time to time. I fixed that and now seems to me it drives evenly. I will make a try whenever possible.

Quick test from my room without a barlow and I could adjust the focuser without much shaking on a star through the window using LifeView on x10 - I wonder if the stable floor made a difference compared to the softer grass outside on the loan.

 

Bahtinov mask - I had made one actually but did not have it with me. Well, mask or not - need to deal with the shaking while focusing still right?

 

For the next try I will remove the barlow as you all suggested. And also adding some more pause between shots to let it calm down.

 

And yes, I AM planning to use stacking but did not want to waste time on it (introducing even more complications) before can get a decent single shot.

 

About EAA - if it's not for Dob then I guess it's not for me - at least at the moment. Actually I am not at all familiar with the process.

 

...

nice first attempt! I can see the cluster

Hey, thank you for the encouragement. With the next opportunity I will make more test shots and let you know the improvement from all said so far.  Also I am aware that my setup is probably what many will consider "the worst" for astro imaging but that's all I have for now and don't mind challenges. Even with a T-shirt you can get high enough to enjoy some pleasant views. Reaching the top I will leave for the pros. 

Extremely helpful forum btw.

 

Greetings

Edited by Branimir, 12 August 2024 - 08:10 AM.

[scanner97]

Lots of helpful suggestions already!

 

If the Dob is your only scope option, what lenses do you already have for the camera?  Unimatrix0's suggestion to try just the camera and tripod might be an easier path.

The lens will determine your potential targets, but probably not M13, which is only about 20'.  Milky Way shots can be quite spectacular with a shorter lens, or M31 heading into the fall with something a little longer.

You'll definitely want to stack, though, since untracked shots will be on the order of a couple of seconds, depending on the lens and target.  (And it can be hard or impossible to get a single exposure that tells you everything is going right.)   Assuming f/2.8, a 24mm would be about 6 sec max, a 50mm about 3 sec, and a 135mm about 1.5 sec.  (With slight variation based on your latitude and target height above horizon.)

 

You'll probably want several hundred images to stack, so an intervalometer is the way to go.  You'll also need to re-center the camera regularly since you aren't tracking, so this isn't a trivial exercise.  If your Dob tweaks don't get you there and you decide to try this, I would second Uni's other suggestion to check out Nico Carver's channel.  He has a lot of helpful stuff, including some examples using Siril and GIMP, which are free.  (The post-processing can take as much effort as the imaging, if not more.  It's hard to do this in a totally casual way.

 

Good luck!

[Branimir]

@scanner97 - I have only the kit lens 18-55. I am aiming at DSO because it goes along with our astronomy classes with the children. Anyway I will try and I am aware it might not be realistic with the setup we have. Then we'll stick to visual and making some sketches. 

 

About the stacking - I got DeepSkyStacker running on my Linux machine and did some tests with it already and I have experience with GIMP but 'several hundred images' - wow is there such a difference between 50 and 250? I read controversial thing online.  

 

Also it seems to me that the EQ platform can be used with a camera tripod as well isn't it? Even have the 3 holes on it (for the dob stand) where the tripod feet can go. I will just have to fine tune the motor.

[Branimir]

I would call it success!

 

Following the advises above this is what I have so far:

 

Here I placed the camera with 50mm lens on the EQ-Platform and was able to do 2m30s exposures without trails

 

Those are through the telescope

 

 

 

[Branimir]

 

 

All Stacked with DSS and post edited with GIMP. 

 

I found a small error on my platform design so after fixing it I expect to get longer exposure times.

Thank you all for your input!

Edited by Branimir, 01 September 2024 - 11:58 AM.

[Branimir]

Oh and there is the moon as suggested

 

Taken through the window of my room 

 

[Tkall]

Wow.  Those are great.  You are a fast study.  Well done.