Prime focus magnification

[neilm]

Okay, the scope is 432mm focal length, with a 10mm EP in place that equates to x43.2 magnification. I've being doing some afocal images with a Nikon P&P, so if I just put then camera up to the EP I get he benefit of the x43.2. The camera has a zoom so I can get some larger images over the standard.

The camera's only 7 mega pixels and is struggling to capture the finer detail, looks absolutely fine through the EP so I'm thinking lets look at DSLR.

If I do this am I going to miss out on the extra mag provided by the EP and I'm just getting what the scope gives me, essentially a big telephoto lens and I'll end up with much smaller images?

Or, the fact that's it's a DSLR as opposed to a P&P will compensate for the basic images size.

Finally! I've searched through the forum I can't see any reference to using say a x2 converter attached DSLR, I used one of these a fair amount in my 35m SLR days, do they not work?

Thanks

Neil

[Bizibilder]

The telescope simply acts just like a camera lens - so you have a 72mm f/6 "lens" on your "camera".

This link: http://new-astronomy-ccdcalc.software.informer.com/

Latest version download, news and info about this Multimedia Madness, Inc. program. The New Astronomy CCDCalc is a virtual astrophotography imaging software. leads to "CCDCalc" which is free and allows you to see how various DSO's fit onto various camera/scope combinations - if yours is not there you can set it up manually. It is really useful for seeing just how "big" or "small" commonly imaged objects are.

[bus_ter]

The 'Magnification' way of thinking doesn't really work in imaging. Different chip sizes, focussed at different points and then ultimately viewed on a computer screen at different sizes means you can make the magnification whatever you want.

Instead you need to be thinking about getting the objects image spread over as many sensor pixels as possible. That's why planets work well on tiny webcam sensors, but don't work on large dslr sensors (pixels are too big for a tiny object). The CCDCalc program should be good at getting you thinking this way.

Yes, you can still use teleconverters connected direct to an SLR. In fact these are usually optically much better than barlows. The camera world has a much lower tollerance for CA and lens distortions etc compared to the telescope world (though that's starting to change..) but remember a cheap teleconverter will cost as much as a very high end Barlow..

[neilm]

Thanks for the info. I've download the ccdcalc software, looks quite nifty, just need the time to spend messing around with it.

Cheers

Neil

[dlp]

I had a look at 2x converters for my D90 the other day. The latest Nikon one, although it boasts to be the first with ED elements, is the best part of £500. Sheesh...