Problems (or features?!) of NexStar SLT Alt-Az mount

[VilleM]

Hello, I have recently started building a portable setup with my 100mm f/5 achromatic refractor. Im using ASI120MM and CaK to capture solar disk with it. However it seems that my mount is not up for the job. Im using NexStar SLT and the image seems to drift very fast out of the view! So fast that I need to apply corrections manually from the handset every few seconds to keep part of the solar disk on the FoV.
Ive set the mount level, it is tracking in Alt Az mode ( I dont have a wedge). Also I tried to take some long exposures with a DSLR and 16mm lens but I only got to about 20 seconds before stars started to drift. I can get 15s subs without tracking at all so its really small improvement.

My question to NexStar SLT owners is that is this kind of behaviour really normal? I would think that even with alt az mount you could get atleast somewhat decent tracking although field rotation will become an issue at some point. Ive never reached that point, everything just seems to drift out of the frame even with aligned goto and correct time / date / location settings.

[banjaxed]

I am not an expert but I think there is a tracking speed adjustment somewhere in the handset settings.

[VilleM]

Indeed there is, its selectable to EQ / Lunar / Solar and Im familiar with it. I think this might be a power problem because when I use battery power with AA batteries the tracking seems very unsteady and seems to stop every 10 seconds or so before moving again. This doesnt happen when the mount is plugged in with an AC adapter. Weird.

[banjaxed]

31 minutes ago, VilleM said:

Indeed there is, its selectable to EQ / Lunar / Solar and Im familiar with it. I think this might be a power problem because when I use battery power with AA batteries the tracking seems very unsteady and seems to stop every 10 seconds or so before moving again. This doesnt happen when the mount is plugged in with an AC adapter. Weird.

It is often suggested that batteries are one of the biggest contributors to mount problems. Maybe stick with an adapter or a decent 12 volt battery to be sure.

[Cosmic Geoff]

I do not recommend the use of AA batteries. The main purpose of the battery holder is to avoid having to bundle a PSU with the mount, which would increase the selling price.  Instead use a +12v 'power tank' or a mains powered PSU.

I have used my Nexstar SLT mount for imaging, mainly with a 102mm f5 achro refractor, but the mount is barely accurate enough for this. It does tend to drift about, and this is also noticeable when using it for planetary imaging with a 127mm Maksutov, where a very small active FOV is used. 

With a 102mm f5 achro + ASI224MC camera, exposures of a few seconds for deep space imaging are possible.

For better imaging performance, you could upgrade to a Synscan EQ-5 mount.  I don't like the Synscan operating system, but with the addition of software and a link cable to give platesolving and resync, the performance is impressive.

[VilleM]

Id love to use mains power or large battery but I try to keep my setup airplane ready and light for travelling. But thanks for the tips, Ill try with a battery next time the skies are clear.