Integrated guide vs separate

[Spocky]

Hello all,

I am a bit new to all this but am looking at getting into astrophotography and just would like to ask some opinion type questions.

What is better for guiding, an integrated CCD (like in the SBIGs) or a separate telescope + separate camera?

I am asking not only on a cost basis but to me an integrated camera would be a better idea because of the resolution axis is the same as the imaging camera and there is no differential movement potential added with a second scope/camera mount.

Does anyone have any issues or problems that I am unaware about?

Cheers Spocky

[Geoff45]

I've never used an SBIG, but I understand that when you use filters, especially NB filters, the filter reduces light to such an extent that it may be difficult to pick up a guide star. This wouldn't apply to a OSC camera

You could look at the QSI cameras, which come with an option for a built-in off axis guider, so your imaging scope is also the guide scope (so no flexure issues) and the pick-off prism is in front of the filters, so you get full brightness through to your autoguider.

[pmrid]

Have you considered an Off-Axis guider. Do a search in these forums on off-axis guiders and you'll find several threads in which they are discussed extensively. Also, have a look at the site of companies like Orion and ATIK both of whom make good OAGs. I have an Orion, a Celestron radial guider and a Lumicon OAG and I much prefer the Orion Deluxe.

With an OAG you have the advantage of eliminating flexure and you also can still use SBIG cameras with filter wheels because these sit behind the OAG. The newer SBIG's can take what they call a remote head which sits in the OAG in the same place that you would otherwise put a small guide-cam like a QHY5 or an Orion.

Hope that helps.

Peter.

[AlexN]

Having used both methods, and also OAG's (being a separate guide camera through the imaging telescope) I must say I like the convenience of self guided cameras.. I have used self guiding through a 13nm Ha filter without too much troubles.. I binned the guider 2x2 and ran 2~4 second guide exposures and had no troubles at all..

I love self-guide!

[strongmanmike]

Hi Spocky

People will tell you that Self Guide is great or even indespensable but from where I stand it is simply not necessary. A good quality mount is very helpful though :thumbsup:

I have used piggyback guiding pretty much for ever and I cannot see what all the paranoid selfguide hulabaloo is all about :shrug:

Here are some comparative examples that should belay any fears you may have about passing up on a selfguided camera :rolleyes:

http://www.pbase.com/strongmanmike2002/image/118094040/original

http://www.pbase.com/strongmanmike2002/image/113745498/original

http://www.pbase.com/strongmanmike2002/image/107605167/original

NB: Out of about 130 X 10min sub exposures taken over three nights for the full deep version of the above Centaurus A image, only about 3 or 4 were discarded due to guide errors!

Even using 15min sub exposures here is what piggyback guiding, when using narrowband filters so notorious for selfguided images , can do:
http://www.pbase.com/strongmanmike2002/image/118318593/original

Think about what these comparisons are demonstraing and make up your own mind :thumbsup:

Mike

[AlexN]

I agree with Mike, in most cases its not necessary, however its sure is convenient... You can achieve just as good results using an external guide scope and guide camera... It sometimes will take a little more time and effort in eliminating any flexture etc. I was plagued with flexture when using my C11 due to its moving mirror... getting a self guided camera eliminated the problems...

My thoughts - Adaptive Optics is -THE- best way to guide... AO surpasses any form of normal guiding, as it reacts much much faster than your usual guiding methods.

[Bassnut]

Beware, Mike is low QE, non-AO capable, wide field wooze, FLI sucker freakoid. "even 15min subs" :shrug:. It gets interesting at 20min plus. Mike doesnt know what 2m plus FL means, he is disabled ;).



OH yeah, if you want to "get real" with long FL/exposures, then AO is the ducks guts, yay SBIG :D

[strongmanmike]

Actually it is Fred who is dissabled by those unecessarily long focal lengths he insists on using to image tiny postage stamp size pieces of the sky that require long sub exsposures becasue of the large dim focal ratios :rofl:

[Octane]

I am literally lmao at the last few posts. :rofl:

More biffo, please!

H

[mill]

Fight! Fight! Fight! :P
Hajime.

[strongmanmike]

Take your pick - who do you wanna believe?

[jase]

Geez, looking at those mugs...don't think I'd trust either. :lol: ;)

More to the point, as Geoff, Peter and Alex have alluded in earlier posts, it depends on the focal length you're operating at. Glen has not indicated this so we are none the wiser in our advice (despite the joyous SBIG/FLI slinging match).

[strongmanmike]

Maaaa I dunno..?

It is not the focal length exactly really but more the fact that if the long focal length is provided by a multi mirrored telescope with truss tubes, inadequate focusers, loose mirror mounts or with floppy mirrors, ie Newt, RC or SCT there is potential for differencial movement over time. The significance of this differential movement is a function of the focal length and your image scale sure but the degree of flexure and the time period over which this movement takes place will depend strongly on the class and design of your telescope and guide scope interface.

It is clear from the above comparisons that self guide is simply not necessary just becasue you have a long focal length, the comparisons show rather difinitively that for 10 - 15min exposures at least, the absolute resolution possible without self guide is clearly equal to that with self guide and even rivales AO, atleast for modest exposure times and with a good quality mount.

Due to the limitaions of self guide (poor transmission through filters and faint or no guide stars etc) there are many imagers (most?) both long focal length and short, with selfguide cameras, who are basically forced (happily) to use piggyback guiding and they acheive excellent results!...why worry about having to have the self guide if piggyback works just as well and you must have a guide scope anyway? this is why I think the self guide feature for most situations is just simply overated.

Don't let anyone tell you that darks will always take care of the noise level in your noisey warm subs either, this is not true, excellent cooling does make a difference this is why cameras with poorer cooling cababilities very often have to resort to messy cumbersome water cooling, and others even resort to putting their cameras in a fridge :eyepop: while imaging :lol:.

Self guide is a feature for sure but there are other qualities in a good CCD camera that I believe deserve more consideration - namely: overall noise levels, cooling abilities, download speed, method of keeping moistier at bay, build quality and reliability.

Mike

[AlexN]

Indeed Mike... Self guide is one of many features to consider when buying a CCD, and definitely not the most important... However this thread is only about self guide vs external.. so lets for arguments sake say that the two cameras we are comparing are an SBIG ST10XME (self guide) and ST10XMEi (no self guide)

Everything else is equal except for self guide... for the tiny extra cost of $200, self guide is worth having as an option... Though its not necessary, its nice to have the choice... Its like going to the pub.. whilst there is no need for them to have 10 different beers on tap, it sure is nice to know you can choose what you want...

[strongmanmike]

But here you are comparing having a selection of one extra beer in two different Sizzlers restaurants when you could be having a choice, all be it one type of beer less, at Doyles by the Sea across the road (but at little extra cost in the CCD analogy)... if you just remember it is there through all the Sizzler hype :thumbsup:

:lol:

Mike

[AlexN]

hahaha... yea man.. that was good, very indepth analogy.. :) Loving it!

The question.. Would I forgo self guide for -60c cooling... Bet your backside I would....

If there was a camera offering both self guide and the sensor I want to use with 60c cooling capacity, would I then buy that? you bet your backside I would.... Why? You all know me, I simply can't help myself thats why..

[Bassnut]

Hence OAG :D



hehe, really ? :lol:, rivals AO ?, at long FLs? :thumbsup:.



Oh really ? :lol:

And a quote from Steve Cannistra
......we don't even need cameras that can cool to -25 C. And by imposing more aggressive cooling on these chips, it is possible that we are increasing the likelihood of experiencing other side effects such as residual bulk image (RBI)

Its OK Mike, you can be wrong. I understand, it proves you are human, dont be embarrised, I forgive you ;). We love you mike, its a momentary lapes of reason thats all. :love:



And you too Alex, behave yourself, stop crawling, its silly ;).

[jjjnettie]

Well, any man who can wear a skirt with as much confidence as Mike, deserves a little respect.:thumbsup:

[AlexN]

I believe the STX-8300 will be released later in the year. At which point, there will be a camera with the sensor I want, -60c delta cooling and self guide :P Crawling?? No, just longing to get self guide back :)

[Bassnut]

hehe, nice pic Mike. Guad youll scare the natives with that, we look like fruitcakes...........umm yeah, well, one of them is anyway :rolleyes: :).

[Bassnut]

Sorry Alex, wrong quote.

"Would I forgo self guide for -60c cooling... Bet your backside I would."

This one is sad, correct yourself or be forever condemed :mad2:. Its appalling.

Of course, STX is the go, and will forever make FLI fanatics jealous, disabled, and forever regretfull of their foolish, foolish choices :rofl:

[sjastro]

A 5nm or less narrowband filter will be a real challenge for finding guide stars.

Steven

[AlexN]

Steven - OAG + RGH for narrowband work. Self guide for RGB data. AO-STX for L data... You know the drill, you use ST10-RGH-MOAG-AO do you not?

Fred - I must have had a few too many beers... I took a series of darks with my ST8300 at -10, and another set at -15 and the ADU counts were less than 50 ADU's apart even at 15min duration... Cooling is required, but there is a point of diminishing returns... SBIG/Self-Guide/AO forever!

[sjastro]

Alex,

I self guide exclusively. That's why I don't do any Ha imaging.

Steven

[Spocky]

Looking at 1000 to 1500mm refractor.

Cheers Spocky

[marki]

AO is no longer an SBIG exclusive...other options are out there.

Mark

[AlexN]

True Marki, I looked at both the SX and the Orion units recently.. Personally, The only reason I'd go near the Orion AO unit is to throw rocks at it. The SXV-AO unit seems quite good, and results I've seen show that its very capable. Until recently they have only been of use to those with APS-C sized sensors and smaller, although reports have it that SX are releasing a new AO unit able to be used on 35mm systems... Neither of these units are as cost effective as the SBIG AO setup, nor are they as well proven in the field.. The SBIG system is incredibly well integrated... I myself have been looking at the SXV-AO unit, as I love my ST8300, but do want an AO option... That said, I'll wait until the STX8300 comes out and go for the AO-STX..

[marki]

I was also considering a SX unit as well.. not sure why you would throw rocks at the orion though, they are soon to release a version which has motorised adjustment of camera and pickoff prism as well. Never the less there will be even more options in the near future me thinks....anyone for -60 and AO.....;). Ps the KAF 8300 is smaller then a APS sensor....just a thought.


Mark

[AlexN]

My reasoning regarding the Orion AO is that it is more expensive than the SX unit, it requires nearly twice the back-focus distance, its quite a bit larger, physically heavier and yet designed to do the same job. When it comes down to it, its a question of who you trust, and what you're willing to pay... Even if the performance was equal... Would you pay more for the Orion option than for the SX option? Also, I've seen results from the SX unit, I've not seen anything from the AO unit, nor have I heard from anyone who uses one...

The Orion one with a motorized OAG rotator seems like a good plan... Implementation is the key, and getting it all finished and in the market without adding 1k to the cost of the unit is important too..

Competition is always good.. the more AO units there are available to us, the better. I just think they should be appropriately priced... If SBIG can do the AO-8 for $795 USD, how does Orion justify $2250AUD for their AO unit?

As you say, -60c and AO is the goal, I'll just wait till I can get it in the most self contained way possible... Which I would imagine will be the STX-8300, STX CFW, STX-AO. Needing only the power and data lead for the camera, everything else plugging into the STX-8300 head, reducing cable clutter between the laptop and the mount, lessening the load on the USB etc

[marki]

SBIG unit is only good for an SBIG camera (small market), both SX and orion are offering units for all types of brands. Still the retention of T2 fittings will always limit their usefulness. I was actually considering the SX FW and OAG at one time.

Mark

[Bassnut]

I was wandering about the Orion AO (and the price), it seems like a very nice unit, with the the rotator, OAG and AO all built in, I dont know why this wasnt thought of years ago, seems obvious. Havent seen any user reports on the web at all (not that I looked for them, just in passing). The BF distance/weight of seperate MOAG, AO8 and rotator is probably more than the Orion?.

[AlexN]

AO8/MOAG/Rotator are probably heavier than the Orion unit, and definitely has more backfocus requirement... but as Marki said, the AO8 setup can only be used on SBIG cameras, so comparing them isn't really worth while..

It is a good setup, all in one. I just wont put any faith in it until I've seen results. The SX unit has been tried and tested. As has the SBIG setups. As you say - no word on the orion AO at all, aside from marketing literature..

[marki]

The version with the rotator is not going to be released until may I think. I read the backfocus requirement was about 60mm.

Mark