Astrophotography Help

[HiDefJef]

Hi All

I'm a little new to this and realise this may have been covered elsewhere but i'm really looking for a definitive answer. I have a Celestron 130EQ Astromaster and would like to use it for photography. I've read on several posts that there is an issue with getting the camera to focus without a Barlow lens. I originally was looking at the combined barlow/T adapter that celestron do but I gather from several suppliers that they're rarer than hen's teeth. Because of that i'm now looking for an alternative and don't really want to shell out a lot of money on equipment I don't need.

The camera is a Nikon DSLR.

Many thanks for any help

Jeff

[barkis]

The problem is, as you probably know, is there is not enough focuser inward travel, to allow an image at infinity (Stars, Planets, Deep sky objects), to reach your cameras sensor.

This is mainly due to the depth of the camera.

If prime focus photography is what you wish to do, the there is one solution to the problem, but maybe not one you would wish to to carry out. That is, to move the scopes Mirror a bit further up the tube, so that focus can reach the camera sensor.

There is a drawback to this method though. Moving the mirror up the tube, may cause vignetting of the light path, as your secondary mirror may not be large enough to intercept all the light, because the light cone will be wider when it reaches the secondary, due to the mirror being closer to it.

This is a solution that needs to be thought hard and long about, and if your DIY skills are lacking, then don't attempt it.

I think perhaps you should perhaps consider Lunar and planetary imaging, which can be done by Barlow, and / or eyepiece projection methods. A web cam can be bought reasonably cheaply, which is more suitable for moon and planet imaging.

Ron.

[x6gas]

I don't know if your 'scope is the same, but on my Celestron C6N you can unscrew the eyepiece holder from the focusser. There is a built-in t-mount and so you just screw in a t-ring matching your Nikon and then attach your camera. On my set-up this gives more than enough back focus for my Nikon D40. Even if you an't do this, it might be worth investigating changing your focusser to one that does allow this.

Your really don't want to be moving your secondary mirror about if you can help it IMHO.

Let us know how you get on!

[barkis]

When I mentioned moving the mirror, I was referring to the primary, not the secondary, which would involve moving the focuser too.

Ron.

[x6gas]

When I mentioned moving the mirror, I was referring to the primary, not the secondary, which would involve moving the focuser too.

Ron.

Sorry, my misunderstanding .

[barkis]

Sorry, my misunderstanding .

No worries mate.

[HiDefJef]

Hi Guys

Many thanks for both replies. I have to say, not what I was expecting but boy you guys know your stuff !

Firstly, Ron, thanks for the really detailed solution but as the scope is less than a month old I don't really want to start making any major changes a) because I don't really know what i'm doing and because it will no doubt void the warranty. I really would like to stick with the DSLR/telescope setup as I think the CCD in a DSLR is going to hopefully give me some really nice images at a good resolution. Ultimately i'd like to publish/print these images so i'm aiming for a reasonably good resolution.

X6gas, i've had a look at some images of your scope and it at least looks similar to mine ( though I think yours certainly looks more upmarket ). I've unsrewed the eyepiece and there is a thread there, though as I don't have a T ring ( yet ) I can't test it. I'm actually spec-ing this out for a birthday present for me ( on pancake day ) so won't be able to test it until then.

I'll post a reply to this in a few weeks time to let you know how I get on.

Many thanks again to both of you for being so quick and detailed in your replies. I knew joining SGL would be a good thing !!

Jeff

[x6gas]

No problem Jeff.

You should be able to get a nikon t-ring from good camera shops for between £10-20, less online. Remember you don't need the t-mount, just the t-ring!

My first attempt at a DSO is in the imaging forum - this is just a first attempt, fairly short exposure of just 30 secs and with lots of rookie errors so the scope is capable of much better I am sure...

[stardad]

Hi All

I've read on several posts that there is an issue with getting the camera to focus without a Barlow lens. I originally was looking at the combined barlow/T adapter that celestron do but I gather from several suppliers that they're rarer than hen's teeth.

Jeff

Try here

Celestron 2x Barlow for 1.25" eyepieces (includes T-adapter) 93640

or here

Celestron 93640

Watch out for the price of postage and customs duty and Royal Mails handling charge.

You could try these guy's

https://www.astronomia.co.uk/astro/index.aspx?pageID=1053&catID=98

as they have it in stock at £93 plus postage or

First Light Optics - Suppliers of Astronomy telescopes, binoculars and accessories from Skywatcher, Celestron, Meade, William Optics, Atik, Imaging Source, Starlight Xpress, ADM, Moonlite, Catseye, Hotech and others. who have it for £91

if you want the celestron part.

I was going with the 2x Barlow and one of these

Adaptors - T Rings

plus one of these

Adaptors - FLO 1.25-inch T mount camera adapter

route's on the same scope but using a Sony A350 camera as a starter. I'm just a little concerned that the CG-3 mount wont take all the extra weight.

[E621Keith]

Not to put you off, but I think the moon is the only thing you can capture with a DSLR and your current telescope. Planets will be too small for a large chip DSLR, a mod webcam will do a much better job.

For long exposure DSO imaging, your mount will be too light. Most people recommend HEQ5 as a minimum astrophotography mount. Most also recommends this book - Making Every Photon Count by Steve Richards.

[HiDefJef]

Hi Keith

That doesn't put me off as the main reason I got the telescope in the first place was to try and get some images of the moon. I studied photography a number of years ago and have never managed to get a really nice shot of the moon. A long lens is out of the question as this would be the only thing i'd use it for and they're expensive, so a telescope seemed to be a good solution, as it gives me what I want and also allows me to look at the night sky ( we live in the country so that skies are as dark as they get in the South East ). Whilst i'm really impressed with the DSO images that others have taken i'm not expecting too much from the setup I have. If I can get some nice shots of the moon anything else would be a bonus.

That said if I get the bug I may be looking to upgrade sooner rather than later !

Thanks for the input

Jeff