Celestron SLT EQ mode

[sgazer]

hi,

not posted for a while and not really had chance to do much astronomy recently due to kids and too many other hobbies, hence I've down-sized my setup and now use a DSLR on my SLT mount. (plus Aussies pay top wack for astro gear, so sold it for a good price). Regarding the SLR mount, I recently read on this site;

http://www.nexstarsite.com/

that you can put the software from the SE mounts into the SLT (NXS software) and then use it in equatorial mode. I gave it a try as I want to remove field rotation and also having the mount track in one axis only (RA) has got to be more accurate than tracking in two axis (ALT/AZ).

I'm pleased to say the SE mount software works in the SLT mount. I built up a wooden wedge which sits on top of the tripod and attached the SLT mount to that. I set it up last night using using South EQ auto align (I'm in Australia) and all went well, gotos were pretty close and I was able to control the mount using CDC with the Celestron ASCOM drivers. With a very rough polar alignment, I was getting reasonable 2min exposures with a 250mm lens. Later, I realised my polar aligment was way off, dodgy compass, so I'll try again with better polar alignment, and in fact I'll try the Align Master software, as it seems so simple to use.

My plan is only to use my 450d on this mount for imaging, and I've got an 85mm f1.4 lens coming from the US for this (which will require 12x less exposure time than my previous f5 scope), hence 1 minute will be as bright at 12mins on the f5 scope, that's the theory at least.

As the 450d has 12MP, it allows for some significant cropping of the image to cover the area of interest.

Hopefully this quick and portable setup will allow me to get more astro imaging done that I could before.

[sgazer]

I guess there's not too many SLT users out there these days, but hopefully someone will find it useful in the future!

[jgs001]

Now that's an interesting workaround... nice job... I did look at something like that, but the SLT wasn't meaty enough to carry what I wanted it to. I may have to dig it out and have another go.

[Cornelius Varley]

Do you have any photos of the DIY wedge ?

Peter

[sgazer]

hi, I'll try to post a picture, but basically, it was just 2 rectangle pieces of plywood joined with a hinge, with an adjusting bolt through the other end. The bottom piece was bolted to the original tripod 'bowl' with long bolts, the top piece had the base and arm attached using the original big black hand bolt thingy.

Actually, although it worked, I've taken it off now. The advantages of equatorial tracking didn't outweigh the time it took to get it polar aligned (up to 1 hour of messing around compared to 5mins for a normal ALT/AZ alignment). As I only need 30s exposures with the F1.4 lens @85mm, the ALT/AZ tracking is sufficient.

John, as you say the SLT is not very meaty and with a wedge it leans quite far over and all the weight is hanging off the already curved arm (it's not possible to reverse it to use the curved arm as an advantage either). It was fine for a camera and lens, but a scope would be pushing it.

[jgs001]

Could you mount a small finder scope along the axis of the wedge to aid in PA ?? It helps with an EQ1. Yeah, I'd forgotten about the curvature of the arm... not used my SLT in ages...