DSLR and magnifications?

[scubaian]

My t-mount arrived today. The only way i can get the camera to attach to the scope is to remove the diagonal plus lenses and attach it directly to the main body of the scope.

This means i cant use any lenses to magnify any images as they cant attach anywhere?

Is this always the case as it doesn't make sense to me that you can take photos but not magnify the image first?

I have a pentax K10d and a startravel skywatcher 80mm refractor and have attached a photo for comments.

I'm a complete novice so any basic tips would be most welcome as i don't understand all the terms yet!

[skywatcher1701]

this is called prime focus, and you telescope is your camera lens, if you want to use your camera lenes, then you could always mount your camera on top of the scope

[scubaian]

I don't want to use the lens, i want to be able to photograph what i see through my telescope using the magnification lenses.

I thought this was the way to do it until i put everything together.

Anyone know what i need to do?

[The Sailor]

With my 1.25 adapter I unscrew it from the camera adapter and put a 6mm inside and screw it back on, refocus and thats it for me, would be glad to hear of other ways.

Jim

[skywatcher1701]

Someone will be along to answer your question soon, sorry could not help, the way you have it set up in your photo is the way that i do it, i then crop the photo in photoshop, and i take more than just one photo of the target and stack then in a program called depp sky stacker, i'm no expert but there are a few on here who will help you even more.

One thing i would suggest to you, if you are going down the slippery slop of astrophotography, you will need a mount that can track for longer exposures, unless you have one already

Good luck

[brantuk]

Take a look at the Baader Hyperion range of ep's. I have the 8-24 Zoom, the 17mm and 8mm ep's, plus both FTR's and the adaptors to attach to a T-ring. All of these can fit in the scope for "eye piece projection" imaging with DSLR.

Alternatively you can get a "Universal Adaptor" which fits on any ep and holds the camera in place at the ep.

They can all be barlowed and filtered too

[brantuk]

Here's a couple of links you may find interesting:

Adaptors

Telescope Accessories | Eyepieces | Baader | Rother Valley Optics

Of course theres nothing wrong with prime focus imaging either.

[scubaian]

Am i reading correctly that i'll need a t-mount that is long enough to hold a 1.25" (lens size for my scope) lens?

The ones on the links Brantuk suggested are a lot longer than the one i bought?

[brantuk]

Scubian - I'll get you some pics when I'm home after work tonight. It all screws together Camera - eyepiece - telescope dead in-line and very easy. But you need ep's with a thread at the top where you look through, and an adaptor ring to size it to the T-ring for attachment to a camera. I'll get a pic of the rig assembled, and another in bits for you.

[scubaian]

Cheers for that, i'm sure it will all make a bit more sense then!

[themos]

I don't understand why you want the eyepiece in the optical "train". The digital camera is a retina, the telescope's objective is a lens, you already have what you need. Are you concerned with image scale?

There's 3 ways of photographing: prime focus (what you're doing), afocal (you point a camera+lens towards the eyepiece) and projection (you do what you're doing but you add an eyepiece that acts as a magnifier). Prime focus is preferred as it involves the least amount of glass.

[scubaian]

Themos,

I don't have a very powerful telescope, therefore the eye pieces and the magnification they bring will benefit any pictures i take. I don't know what magnification i'd get just using the scope and camera, therfore i'd like to use the lenses also?

I don't know if i need the eyepiece in the optical train, just want to know how to set up my camera so that the eye pieces are in use to magnify any image.

[brantuk]

The way I'm reading his request is that he wants to do eye piece projection - I could be wrong of course

(Edit) Ahhh... looks like I read it right lol

[Whippy]

I think you may well be best served by doing a bit of reading on the subject. By all means connect everything together and have a go but imaging can be a complicated and frutrating past time. Trust me!

My fellow moderator steppenwolf has produced an excellent book for beginners on the subject and I heartily recommend it. Details here: Beginners guide to astro-photography .

Tony..

[ollypenrice]

Hi and welcome to the sinister world of imaging...

There is no such thing as a 'powerful telescope' in imaging and the term 'magnification' has no meaning! Let's see why;

-Forget magnification because it depends on how big your print is, or your screen, or how zoomed in you are on your screen etc.

-Instead think of image scale (professionally known as Plate Scale.) This relates the size of the object on the sky to the size of its image on your chip, respectively measured in arcseconds and mm.

-Now distinguish between the quite different needs of deep sky imaging and lunar-solar-planetary. Deep sky first;

-Your target objects are quite big. The Andromeda galaxy at prime focus (I think your scope is an ST80?) will just squeeze onto your chip. No need for more image scale, then, on thousands of DS objects. For reasons that will become clear, if you want to image smaller objects you will need to buy a scope with a longer focal length.

-So your targets are large but they are also faint. Problem! To image them you need a fast focal ratio. You do not need more aperture. Focal ratio alone determines the light intensity falling onto your chip. I know it sounds crazy but it is true. If your scope is an ST80 at f5 it focuses an intense beam onto your chip. Good!

-The bad news; you cannot just put in a lens (EP or Barlow) to image smaller deep sky objects and make them larger on your chip because you would drop the focal ratio below the critical level for deep sky work. F5 plus 2x Barlow = f10, right on the bearable limit. I call a halt at f7.5 myself. Your object would indeed fill more of the chip but it would become horribly faint and exposure times would become impracticable.

So now for planetary imaging. Here your object is tiny but very bright. Bright enough for very slow focal ratios to be okay. Here you can put in Barlows, TeleExtenders and Eyepieces and still get enough light intensity for your image to work out fine. It will have the image scale needed to show detail on your picure.

Now an ST80 will get you started but there is a problem. It is a very fast refractor at f5 and this creates a range of problems for the designer. Keeping the field flat (round stars in the corners of your chip) and getting all the colours to the same point of focus are both very difficult. F5 (ish) refractors for imaging are about the most expensive optical devices on the planet, per unit aperture! I have a similar sized, similar f-ratio Takahashi and it cost 35 times what I just paid for an ST80 from FLO. There is a reason for this...

But the ST80 will get you started and working in astrophotography.

I don't do planetary imaging myself so others will give good advice on that side.

Olly

PS Edit. Anything written by Steve (Steppenwolf) is worth reading, I heartily agree.

[brantuk]

Yes - I just got that book a couple of weeks ago and it really is good. It takes you through everything you need to know in a very readable and easy to understand style. I recommend it too

[brantuk]

Hi Scubiain - here's my first arrangement using a universal adaptor to join the e/p to the camera. Together and in bits. Sorry if some pics are a bit blurred:

[brantuk]

This next one is using (L to R) Camera, T-ring, 58mm step down ring, and the Hyperion Zoom:

[brantuk]

You get the idea - the next one I've just shown the bits for camera, T-ring, 54mm step down ring, 17mm Hyperion e/p:

This final one is a Skywatcher Field Flattener which has a T-thread at one end attached direct to the camera:

You can see I've used a combination of 1.25" and 2" attachments so you are aware of possible combos. These of course all go straight into the focuser tube or diagonal (or 1.25" - 2" adaptors) and all bits are threaded for filters. There are other types of adaptors - this is just a small selection.

I would add that you should read Olly's post above and take everything said on board - he know's what he's on about

[brantuk]

I've just remembered - there's a free application called "CCDcalc" - it's great for showing what the chip will see under different magnifications. You can put your own telescope, camera and magnication details into it (unless allready there) Here's a link:

The New CCD Astronomy Home Page

[TheThing]

Wow, thanks Olly. That us a clear and concise explanation that even I could understand. Cheers for posting, it will make life easier for lots of people.

[astroimpulse]

Agreed! Nice one Olly

And also, BrantUK...very helpful I'd say

[scubaian]

Thanks all.

Brantuk, The pictures and links you've posted are superb, thank you so much.

I'm off to look for some extra bits now!

[brantuk]

You're very welcome - one additional note is that using "prime focus" (your original connections) some people put a barlow between the camera and scope to get magnification.

Glad I could help

[black5f]

Sorry late but the pic in your first post seems to show the T2 thread is in on the eyepiece holder? I av a 150p and you can get a T2 adapter on the scope and the EP holder (just). Ebay sell cheap extension tubes, no af, just large diameter tubes with the right bayonet, just got another set £6.79 inc delivery. They make excellent eyepiece projection adapters!