DSOs are too small

[Currently_existing09092010]

I recently borrowed a friend's canon 550D and took some pictures with it using a SW 200/1000 and a GoTo mount. Focuser is damaged so images may not be the best.

M27 30s exposure 1600 ISO unprocessed

M57 30s exposure 1600 ISO unprocessed

This is the one I would like to talk about. I would say that as the second night out with this DSLR the image is pretty good! But the problem is that it's a bit small. The thing is, i want to switch from this 8in telescope to a WO 61mm Zenithstar which has almost 3 times less focal distance. Now i'm not sure if the FD is the problem, but if it is do i still buy the Zenithstar?

                                                                                                                                                                                                                                                                                                  

 

                                                                                                                                                                                                                                                                                                                                Thanks in advance, George

[900SL]

DSO's vary in size, quite significantly. The size is typically given in subtended angle.

Both your examples are small nebula, and you typically need a long focal length to see these at a reasonable scale (more accurately, image scale and aperture)

The Zenithstar is a short focal length ('wide field') so these types of objects will be very small. A wide field refractor is best suited to larger DSO's like the North American nebula, Elephants trunk etc

Go here and play around with camera and focal length and target to get an idea of what you will see

https://telescopius.com/telescope-simulator

[AstroMuni]

8 minutes ago, Currently_existing09092010 said:

The thing is, i want to switch from this 8in telescope to a WO 61mm Zenithstar which has almost 3 times less focal distance.

Have you used this tool? It helps you visualise what you can hope to capture in your FOV. https://astronomy.tools/calculators/field_of_view/

[Currently_existing09092010]

47 minutes ago, 900SL said:

DSO's vary in size, quite significantly. The size is typically given in subtended angle.

Both your examples are small nebula, and you typically need a long focal length to see these at a reasonable scale (more accurately, image scale and aperture)

The Zenithstar is a short focal length ('wide field') so these types of objects will be very small. A wide field refractor is best suited to larger DSO's like the North American nebula, Elephants trunk etc

Go here and play around with camera and focal length and target to get an idea of what you will see

https://telescopius.com/telescope-simulator

Thanks! What if i get a barlow? Let's say 3x. Would i get about the same size without changing the quality of the image? 

[Currently_existing09092010]

53 minutes ago, AstroMuni said:

Have you used this tool? It helps you visualise what you can hope to capture in your FOV. https://astronomy.tools/calculators/field_of_view/

Thank you!

[900SL]

2 minutes ago, Currently_existing09092010 said:

Thanks! What if i get a barlow? Let's say 3x. Would i get about the same size without changing the quality of the image? 

You would get three times the size, but a barlow reduces the light intensity, so it would be 9x dimmer (area thing). So basically you would see nothing, and you would have issues ensuring guiding/tracking at the extended focal length

[Elp]

An APSC sensor is quite large, so small targets will be even smaller on them.

I used my Z61 to image M27 dumbbell the other night with my 183, it was fine, the camera also has the resolution to support a decent 2-3x crop, one of the reasons I bought it. You will however have a similar issue to your current problem if using a DSLR, cropping will be needed, but more so as apsc Vs a 13 x 9 sensor is very significantly larger, and your pixels are larger too so sampling may become an issue.

 

Edited September 5 by Elp

[Stuart1971]

A nice 8” SCT scope is great to start out with on objects like the ones you pictured, in fact it was my very first scope 26 years ago (and I still own it) a Meade LX90, f10 2000mm fl, also M27 was my very first imaged DSO with an unmodified cannon DSLR, and here is it, it was cropped in about 30%, it’s not great but was from 26 years ago and was my first, so I was and am pretty pleased with it…👍🏻

 

Edited September 5 by Stuart1971

[Vroobel]

2 hours ago, Stuart1971 said:

A nice 8” SCT scope is great to start out with on objects like the ones you pictured, in fact it was my very first scope 26 years ago (and I still own it) a Meade LX90, f10 2000mm fl, also M27 was my very first imaged DSO with an unmodified cannon DSLR, and here is it, it was cropped in about 30%, it’s not great but was from 26 years ago and was my first, so I was and am pretty pleased with it…👍🏻

 

I would say it's excellent! A quarter of century means a huge progress in every aspect of astrophotography. You didn't have PixInsight and BlurX nor NINA, ASIair etc., I'm not sure about guiding. So, guys, appreciate what you have now, a lot of that is free, including the knowledge available on YouTube! 😉😊

 

Edited September 5 by Vroobel

[bosun21]

Your image of M27 is really faint for a 30 second exposure. I can see it better through the eyepiece in my scopes. When doing EAA after 6x5 second exposures I have a well formed and bright image. What is the bortle rating of your skies? IE:- how bad is the light pollution?

[Currently_existing09092010]

7 minutes ago, bosun21 said:

Your image of M27 is really faint for a 30 second exposure. I can see it better through the eyepiece in my scopes. When doing EAA after 6x5 second exposures I have a well formed and bright image. What is the bortle rating of your skies? IE:- how bad is the light pollution?

Where i live it says i have bortle 5 skies, but when i'm looking at the dumbbell nebula i'm looking right towards the city

[bosun21]

1 hour ago, Currently_existing09092010 said:

Where i live it says i have bortle 5 skies, but when i'm looking at the dumbbell nebula i'm looking right towards the city

That probably explains a lot. I am in bortle 5-6 as well.