what magnification do you get with a dslr and 10" newt?

[bartman]

Hi Guys and Girls,
I was just wondering what kind of magnification you get when attaching a dslr (Nikon d90) to a 10" Newtonian.
i have seen pics of say....Jupiter, (with all the bands, red spot and moons) and they are clear as, full screen and all done with the equipment above.
I realize filters have been used....but I cant understand that no Barlow, eyepiece or camera lens has been used....
Or am I mistaken?
How do they/you guys do it?
Bartman

[[1ponders]]

Bart the telescope IS the camera lens. In that case it's a 1500mm telephoto lense. Using cameras the usual description is area of coverage in arcmin rather than magnification. However to give a rough answer to your question, about 45x magnification for a Canon DSLR and a 10" f/5 newt

[bartman]

Doooh....... should of thought of that!
I'm just attaching a lens to the camera!
Soooo how does one get an astropic of a dso with a dslr attached to a 10
" newt at 45X?
45X ( to me) doesn't sound like a high magnification to get those wonderful pics you see posted on the website.
Can I make a guess that it has to do with autoguiding, filters, cropping, stacking and zooming in on pics taken?
I just cant get my head around the fact that pics of say the horse head nebula can be taken with a dslr on a scope of that size.
I'll certainly keep trawling the forums for info on what others are doing, but if you have a link to an astrophotography 101 howto for dummies, it would be most appreciated:)
Bartman
PS I have had a look at some "how to" sites, but i feel that sometimes they skip stuff.... like the questions I just asked. Is there maybe an intermediate step that I need to explore?

[Terry B]

The magnification is correct. The important measurement is arcsec/pixel
This depends on the focal length of the scope (not the diameter) and the size of the pixel. Maximum resolution of a lens does depend on the diameter of the lens.
Big scopes have better resolution (with some other factors also coming into play) allowing more "magnification" ie using a longer focal length or smaller pixels. (same effect)

[toryglen-boy]

you would be surprised, 45x is about right for capturing larger DSO's, like it woudl be ideal for M8, M20, NGC253, M33, M52, M45, M16 etc. etc. but some people need MORE magnification for smaller objects, planetary nebula and galaxies come to mind.

The Horsehead (IC434) is quite a faint object, and many exposures have to be stacked for a good image, with a 10 minute exposure i can see a faint outline of it, although most DSO's can be seen with exposures between 2 and 6 minutes. If you have good polar alignment, and a good mount, then you can do unguided exposures of about 2 mins, that can be quite good, JJJJ does (did!) unguided subs, and her work is very good.

its all swings and roundabouts

;)

[[1ponders]]

Is you 10" newt on an EQ mount or is it Dob mounted. If its dob mounted then you might want to have a scan through Mikes article on Astrophotography with a Dob (http://www.iceinspace.com.au/63-201-0-0-1-0.html).

To work out the "magnification", basically an old fashion 35mm film with 50mm lens is about 1:1 with the human eye (this is so very rough) so if you are using a 1500mm lens then the mag is approx 30X. Because there is a 1.6 "crop" factor (someone is sure to jump down my neck for using that term because it's not really, but what the hell. :lol: ) multiply the 30 x 1.6 and you get 48X. Really we should be looking at the size of the imaging chip and the dimensions of the scope to be working out the FOV.

eg Canon 20D with 3520 X 2344 pixels with pixel size of 6.5 micron gives a pixel scale of 1.05 arcsec/pix with an f/5 250mm newt. The total field of view is then 61.9 arcmin x 41.2 arcmin. These figures are far more useful than magnification. Knowing your FOV in arcmin helps to work out what object will fit in that FOV. For Example you would fit M42 ( maybe only just) in the FOV but not both M42 and M43, that would require 90 x 60 arcmin (or close to that).

[jjjnettie]

Most of the planetary images you see of Jupiter and Saturn have been taken with a CCD camera of some sort. To get up close and personal you have to use a barlow or powermate to magnify the view.

[stephenb]

Try CCD Calc by Ron Wodaski

http://www.newastro.com/book_new/camera_app.php

Plug in your OTA and camera specs (webcam or DSLR) and it wil give your a visual representation of the view, plus the FOV.

[bartman]

Wow, thank you everybody!
Didnt expect this much response!
Anyway I'll take all your advice's and put them to good use....Its been a while since i worked with calculating angels etc. Time to get the scientific calculator out. I havent had a chance to take the scope outside yet as the viewing conditions here in Perth have been dismal over the last week- and I have had the scope for just over a week now.

1ponders - I have a SW 10" BD on a NEQ6 PRO mount. The camera is a Nikon D90 4288X2848 pixels and pixel size of 5.5um (i believe). According to Ron Wodaski's ccdcald it gives me a fov of 44.9X67.5 arcsec.
Looks good on the preview!

Once again peoples thanx!
Bartman

[bmitchell82]

CCD calc is the best for doing just that calculation! my canon 40d and 10" f4.7 newt runs approximately 60x40 arc second FOV. and it doesn't fit all of M42 in :( ( i only just found this out last week :)

[Starkler]

You dont get 'magnification' with such a system. The pertinent question is "what field size in degrees will i get with this telescope/camera?"