Next equipment purchase, very confused..

[EzyStyles]

Hi Guys, I stand confused right now as to what to do next. I just need some advice on my situation as im tempted to get all of them but due to lack of funds and other piorities, i have to stick to only one option :(

Im kinda leaning towards the DSI 2 if I sell my DSI 1 as im use to the software for it. With a DSLR, I have no experience whatsoever with the settings, software etc so might find it hard to use but the photo quality are fantastic. With the ED80, I feel it will be nice to take widefield shots with the DSI combined.

Please vote so i can get a rough idea.

thanks.

[[1ponders]]

Keep the DSI for autoguiding and get the 350D

[Starkler]

The ed80 will give you a focal length of 600mm compared to the 800mm of your current scope, so not a big difference in field but much longer exposure time.

Will the 350D come to focus in your newt?

[EzyStyles]

I wish I could Paul, but i'll need the funds from selling it to get the 350d :(

[EzyStyles]

noobie question: so no big difference in field of view with the DSI on the ED80? not quite sure if the 350D will come to focus in my newt :shrug:

[EzyStyles]

argh stuffed up on poll 2. It should be: "Sell DSI for 350D $850".

[janoskiss]

Exposure time will be nearly double with the ED80 (goes like the f-number and the ED80 is an f7.5).

I believe that the DSLR in the f/4 Newt will give a wider FOV than the DSLR would in the ED80. But coma will probably be an issue with the Newt + DSLR combo. You've got to do a lot more homework to be able to make an informed decision.

All that said I would get the DSLR, just because that's at the top of my own wishlist atm. ;)

[acropolite]

IMO get the 350D and keep the DSI as Paul suggested Eric, if you don't have the funds for the 350D then wait, the sky will still be there in a few months; even a year. The price of the 350D will probably drop as well.

[Starkler]

No Steve, the determining factors for fov are focal length and chip size only.
This is analogous to focal length and eyepiece aperture stop.

Exposure time vs f-ratio is a constant, so for any given focal length increased aperture gives faster f-ratio enabling shorter exposures.

Im thinking that the DSLR may still give superior images to the DSI in the newt. If you can crop the comatic edges and still have a wider fov and higher resolution than with the DSI you are in front.
Somebody more familiar with the chip sizes and pixel counts may be able to shed light on this.

If this is a goer, at least Ezy can get an incremental benefit, rather than buying an ed80 and going backwards with the DSI. :shrug:

[JohnG]

The Canon EOS 350D array is:

3456 x 2304 Pixels

6.4 x 6.4 Microns

JohnG

[janoskiss]

Yes, I was meant to write DSLR+Newt vs DSI+ED80 - the options Eric is considering. :doh: Probably larger FOV from the DSLR+Newt combo, because the DSLR would have a larger chip.

[Striker]

350D:thumbsup: :thumbsup: :thumbsup:

No need to say anymore.

Sell the DSI if you wish as you can get a cheaper guide camera's anyway.

[ving]

where do ya get a 350d for $850?

[Lester]

Hi Eric,

I voted its up to you. But If I had to say one it would be the 350D, which would be very versatile= P.F through your f4 scope or wide field with lens.

[[1ponders]]

Fov Deg = w/F x 57.3

F= Focal length
w= length or width of chip
both units the same, usually mm
There for Fov for newt with 350D = 22.2/800 x57.3 = 1.59 deg wide
by
14.8/800 x 57.3= 1.06 deg

[Starkler]

Does the 350D have smaller pixels than the DSI ?

[Striker]

DSI = Pixels 510 x 492 pixels (250,000 pixels)
Pixel Size (in microns) 9.6 microns (W) x 7.5 microns (H)

Canon 350D) 3456 x 2304 pixels 6.4 x 6.4

[janoskiss]

There you go. DSLR has a huge field compared to the DSI! Over 4 times as large. So even if you need to severely crop the image to keep coma under control you'll still have a much bigger FOV (not to mention much better resolution). So go get that 350D! That's an order!! :lol:

[Striker]

Ezy...here is your FOV on M20 using both the DSI and 350D with your 8" Optex F4...no focal reducers...just prime focus.

[Starkler]

Next consideration:

Will your optex scope carry the weight of the 350D ?
If its a typical chinese r&p focuser it might be advisable to upgrade to a crayford. I've heard that optex are made by gso, so the gso crayford might be a drop in replacement.

[janoskiss]

Are you sure that simulation is right Tony? The res and pixel size numbers in your previous post would imply a much bigger difference.

[Striker]

Your right Steve...I put the pixel size instead of the chip size for the DSI...my mistake...changing it now....thanks

[EzyStyles]

thanks for your help guys! apologise for the late reply, have used up my internet bandwidth so im capped. really slow.

ok, canon 350d it is! will need to wait abit until my friend comes back from his honeymoon. He works at canon headoffice so thats why i can get it at that price. also, would i need other accessories with a DSLR? i have never in my life use a DSLR before so im truely a newbie when it comes to it. a bigger memory card? extra battery? or can i get some sort of cable which gives me permanent power?

I think my optex is made by GSO not 100% sure on that. the R&P focuser isnt all that good so might need to replace it if i plan to go ahead with the DSLR. its only a 1.25 focuser. Thanks tony with the diagram comparison. It really help me understand what im going to expect from a DSLR compared to a DSI. I know the DSI 2 has a larger chip than a DSI 1 not sure how that will compare with a 350d?

cheers all.

[Striker]

Eric...I did another comparison with the DSI 2 specs as well...it makes little difference to image size and FOV...only slightly larger.

Most site's try to get you stating it's a 8mm Diagonal chip....making you think the chip is much larger...nobody measures the chip size with diagonals always Width & Height.

DSI 2
Dimensions of chip: 5.59mm (w) x 4.68mm (h); 1/2" (8mm diagonal)
Pixels: 752 x 582 pixels (437,664 pixels)
Pixel Size (in microns): 8.3 microns (w) x 8.6 microns (h)

[EzyStyles]

thanks for your help Tony. I've save the pic for my reference :)

been doing abit of researching around, i think I can't afford a DSLR even though the poll suggests i should get one instead of a DSI 2. I probably can afford just the camera on its own but seeing that I will need additional accessories eg: cables, softwares, memory card etc, that will certainly blow my budget way out which is the $1000 mark unless someone wants to sell me their canon 350d with accessories for $1k? :P

I have also sold my DSI :( won't be imaging for awhile now which kinda makes me depressed abit. The last night with the DSI I managed to take 10 objects so i guess i can play with those pics for awhile. My mind keeps telling me DSI 2 DSI 2 DSI 2 . Someone is talking in me but i know a DSLR is the way to go.

what to do now... what to do.

[Striker]

If you cant afford a DSLR then hold off until you can afford the DSLR......you wont be dissapointed.

But its your money so spend it as you see fit.

Good luck.