What effect will not having a guide scope have?

[KingAndromeda]

Hi going to be using the NEQ6 with the 200P to image but without a guide scope and camera. I've been told tracking with the mount itself isn't as accurate than tracking with a guide scope. If this is the case how long of exposure would be the max amount of time be ? - if that makes sense ? Rather of topic but for instance if i aimed to to gather a total of 60 minutes exposure time using 4 minute subs would the outcome be the same a collecting 60 minutes of exposure using 2 minute subs ?

Thanks - Alex

[long_arms]

You can use the finder scope on the 200p as a guide scope, if you source a suitable small camera to use as a guide cam (cheapish webcam possibly).

Dan

[Naemeth]

From what I understand, longer subs are nearly always better, as they have a higher SN ratio (Signal to Noise: i.e. the image will be less noisy with a high SN ratio than one with a low SN ratio. Think the image quality difference between a normal webcam in daytime and a DSLR and it becomes clear ).

[lukebl]

Without guiding, and even if you're well polar-aligned, I think you'd struggle to get even 30-second subs with the focal length of the 200P. Guiding is essential for longer exposures, I'm afraid.

[johnrt]

No a collection of lots of short subs will not give the same result as an equal imaging time in fewer long subs. The number of subs is to reduce noise v's the signal in the image. The only way to capture faint DSO's is with long subs, and then plenty of them to reduce the noise in the image.

What does a guidescope do?? It watches the movement of an individual star and sends corrections to the mount when it moves away from it's original position. An unguided exposure will show errors in tracking long before a guided one, but that doesn't mean you can't get decent 2/3 minute unguided exposures with very good polar alignment and balancing of a small light scope.

DSO imaging is all about exposing for as long as you can manage before your mount shows tracking errors - that is why imagers prefer small light scopes that will not tax their mounts, your planned imaging scope is large and heavy and will show errors in your mount tracking after a couple minutes unguided.

[Brinders]

I remember I was able to get 60 second subs when I had my EQ6 Pro mount using only polar alignment.

Brinders

[Freddie]

For a first go at imaging, a 200P is not really your best option. As already said, without guiding at that FL you will be really restricted by sub length.

[ArmyAirForce]

I could get up to 2 minute exposures with my NEQ6 and F5 200PDS. I now have an off axis guider and Lodestar guide camera so I don't have the weight and hassle of an extra scope.

[nameunknown]

A lot depends on what you want to image. If you are doing the moon and planets (Jupiter, Saturn) and you are using a DSLR that can take a few minutes of AVI, then you don't need accurate guiding and can post-process with REGISTAX to get some quite good results. If you are going for DSO's you'll need lots of longer exposure times and accurate tracking/guiding become important. I use an OAG, Opticstar AG-130M COOLAIR and PhD on my 200pds, as I wanted to keep my Red Dot Finder, didn't want to drill holes in the tube to fit a guide scope back on and with all that weight hanging on the eyepiece wanted to guide from close to the camera to avoid and flexing problems. Also as you'll see from the pic on the left, by OTA is mounted rather high up to give me a fuller sky, so a guide scope up the front end is usuallly out of reach anyway - no such problem with the RDF.

see also: and related posts

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