Blurry Images

[Maira]

Hi,

I recently bought Celestron Astromaster 130 EQ and I am new to astrophotography. I have Nikon D3100 and I got a T-ring and a T-adapter to get started with it but my dslr doesn't focus at all! It is really heartbreaking Can anyone please help me out with this problem? 

Maira

[Atreta]

I had that same problem with my litte 4.5" skywatcher, it only focus with my dslr if i use a 2x barlow lens.

the options for me  were :

finding a low profile focuser( it was more expensive than the scope itself)

move the mirror up( the 4.5" scope  mirror is fixed, so no go), maybe your telescope has the adjustment bolts in the bottom, if it does you can try moving it up a bit, don't know exactly how much, but i'm sure someone knows how much and will help with it

 

 

[D4N]

The 130 newts are a little short of focuser travel unfortunately.

I made some modifications to my focuser to get more inward travel by removing unecessary plastic.  I'm not sure it this is possible with the Celestron version.

[John78]

I had to chop 35mm off the end of my 130P tube to reach focus with a canon 1000D, its quite easy to do, the metal is so thin you could probably cut it with a good pair of scissors.

 

Caution that if you do mod it, eyepieces will no longer focus without an extension tube, the focuser tube will stick a long way out inside the tube (needs modding also really) and most importantly, you need a way to recollimate the scope.

[Victor Boesen]

It is because the astromaster has a corrector lens in the focuser (x2 Barlow) the same problem I have. If you move the lens you can't do any imaging or visual observing...

[Cornelius Varley]

2 hours ago, Bossen said:

It is because the astromaster has a corrector lens in the focuser (x2 Barlow) the same problem I have. If you move the lens you can't do any imaging or visual observing...

The Astromaster 130 doesn't employ a corrector lens in the focuser tube. The Astromaster is a normal Newtonian telescope. not a Jones-Bird reflector which do use a corrector lens. The problem with the Astromaster and most Newtonian telescopes is that they are designed for visual use not imaging. Reaching focus with a camera is usually achieved by using a barlow lens to move the point of focus outwards. Another way is to move the mirror up the tube a few centimetres which is reversible. Hacking bit off the focuser is a bit drastic and would immediately invalidate the warranty.

[alacant]

Hi. Is the clue in the post title perhaps? If the mirror has a spherical figure it's not going to focus with a dslr, back focus or not. HTH. 

[Cornelius Varley]

9 minutes ago, alacant said:

Hi. Is the clue in the post title perhaps? If the mirror has a spherical figure it's not going to focus with a dslr, back focus or not. HTH. 

No. The Astromaster 130/650 uses parabolic mirrors. A spherical mirror would not cause this problem. The problem is common to many reflector telescopes.

[alacant]

It's listed as spherical, e.g. 

Technical Data:
-- Aperture 130mm / focal length 650mm
-- 130mm spherical primary without corrector

I think it may cause blurry images. Not to look through at low powers, but on a photo only bits of it will be in focus. I'm no expert. Cheers

Quote

 

 

[Cornelius Varley]

There has been some confusion about this in the past, even Celestron get this wrong, but the Astromaster does have a parabolic primary- just like the SW130/650 (might even be the same mirror set). Blurry, out of focus images wouldn't be caused by a spherical primary. The problem is down to the distance between the primary and the secondary mirrors, which is a common problem with most small reflectors.

[Cornelius Varley]

21 minutes ago, alacant said:

It's listed as spherical, e.g. 

Technical Data:
-- Aperture 130mm / focal length 650mm
-- 130mm spherical primary without corrector

I think it may cause blurry images. Not to look through at low powers, but on a photo only bits of it will be in focus. I'm no expert. Cheers

 

You should read the full description. It actually states the telescope has a parabolic mirror in the title.

[Adam J]

Firstly the shape of the mirror is irrelevant to this problem. 

Am sorry to say that I am going to have to inform you of some hard truths here. 

Your problem is that you do not have sufficient inwards travel on your focuser (travel towards the scope) to enable you to focus on the plane of the sensor as this is quite far back within the body of the DSLR. 

Some short Newtonians have focusers that are designed to allow you to do this (Skywatcher 130PDS for example), some do not. Unfortunately your telescope is not suited for use with a DSLR camera without significant modifications.

If you are going to image planets or the moon you may be able to focus by using a  2x Barlow lens as others have suggested. Nothing wrong with this as you would most likely want to use one anyway for planets....less so for the moon.  

However, you are not realistically going to be able to image Deep Sky Objects with this setup as the mount is unsuitable for long exposures. 

In the end you do have some options but most of them are going to involve spending lots money.

If you where sold the scope as being suitable for DSLR astro-photography you should complain and send it back.  

If you want to do planets get the barlow. 

If you want to do Deep Sky Objects then you need to do lots of research, cut your losses and save up for better equipment. Personally in this instance I would keep the scope and do some visual observing with it while saving up for a dedicated photography setup. 

I know that is probably not what you wanted to hear, but better to know now than to struggle on trying to make it work. 

*****CUTTING THE FOCUSER TUBE INSIDE THE SCOPE WILL NOT GIVE YOU MORE TRAVEL********** 

 

Adam 

 

 

 

 

[MattJenko]

All is not lost. You can do some DSLR imaging with this scope for DeepSkyObjects, you just need a barlow lens to shift the focus point out of the tube a little.

A lower profile focuser might work, but a simple x1.5 barlow will certainly work.

With this setup, you will be able to get some 10-30 second exposure DSLR images for stacking, even on the motorised mini mount for the scope. This will allow you to get some shots of brighter DSOs and will certainly get you on the path of astroimaging and will allow you to get something out of what you have before making a leap into more dedicated astrophotography kit.

The prognosis for planetary imaging is significantly better. For this you want to use a stronger barlow anyway (or the 1.5 from above to begin with) to make the planet appear bigger on the DSLR sensor. You then use your DSLR to take a video of the planet/moon and follow a planetary processing workflow to generate the image from that point onwards.

[D4N]

I don't think it is as simple to modify the focuser on the Celestron Astromaster 130 as it is on the Skywatcher Explorer 130P, the focuser assembly appears to be moulded into the same piece of plastic that holds the secondary mirror and finderscope.

It would also appear that it does have erecting optics in there since Celestron advertise it as having a correct image for terrestrial use.

Moving the primary up the tube is probably the only option if you want to use a DSLR without a Barlow.

Unlike the Skywatcher variant Celestron don't tout it as being ideal for astrophotography, of course the 130P is fine provided you are using a webcam or planetary camera that can get close into the focuser.  I imagine the same may be true of the Astromaster 130, DSLR's require a lot of back focus, planetary imaging cameras do not.

[MattJenko]

48 minutes ago, D4N said:

It would also appear that it does have erecting optics in there since Celestron advertise it as having a correct image for terrestrial use.

 

This is merely because one of the supplied EPs with the scope is an erecting one.

[Adam J]

58 minutes ago, MattJenko said:

All is not lost. You can do some DSLR imaging with this scope for DeepSkyObjects, you just need a barlow lens to shift the focus point out of the tube a little.

A lower profile focuser might work, but a simple x1.5 barlow will certainly work.

With this setup, you will be able to get some 10-30 second exposure DSLR images for stacking, even on the motorised mini mount for the scope. This will allow you to get some shots of brighter DSOs and will certainly get you on the path of astroimaging and will allow you to get something out of what you have before making a leap into more dedicated astrophotography kit.

The prognosis for planetary imaging is significantly better. For this you want to use a stronger barlow anyway (or the 1.5 from above to begin with) to make the planet appear bigger on the DSLR sensor. You then use your DSLR to take a video of the planet/moon and follow a planetary processing workflow to generate the image from that point onwards.

Yes you can do some DSO's, I guess that you can do some objects like clusters or the brighter parts of M42 using short exposures, but even 30s is pushing it with that focal length and no tracking.  A 1.25inch 1.5x barlow will cause horrible vignetting on a DSLR and reduce the optical speed of the system. So yes some DSO's are possible using the Barlow but the results may not match the expectations. 

Observing or Planetary are a much better prospect with this equipment. 

[MattJenko]

2 minutes ago, Adam J said:

Yes you can do some DSO's, I guess that you can do some objects like clusters or the brighter parts of M42 using short exposures, but even 30s is pushing it with that focal length and no tracking.  A 1.25inch 1.5x barlow will cause horrible vignetting on a DSLR and reduce the optical speed of the system. So yes some DSO's are possible using the Barlow but the results may not match the expectations. 

Observing or Planetary are a much better prospect with this equipment. 

The Astromaster 130EQ does come with a little motor option, so can do RA tracking, albeit a bit hit and miss from memory. Your conclusion about observing and planetary being the better bets are still true though.

[Cornelius Varley]

Another option is to use an eyepiece projection adapter https://www.amazon.co.uk/Adapter-Telescope-Camera-Eyepiece-Projection/dp/B00KQGV91W/ref=sr_1_2?ie=UTF8&qid=1473857637&sr=8-2&keywords=eyepiece+projection+adapter . A suitable eyepiece is placed in the tube and the camera body attached using a t adapter, the unit is then placed in to the focuser.