Guide scope choice

[Anthonyexmouth]

what would be the best choice for my HEQ5/ED80

SW evoguide ED50 or an ST80 to pair with my ASI120MM. Or is there an even better option in that price range?

[wimvb]

Many imagers use a finder guider with the ed80, with good results. But if you plan to upgrade your scope to a longer fl at some point, an st80 for guide scope may be a better solution. With guiding equipment it's very much "if it ain't broke, ..."

The shorter fl of the guide scope makes it easier to find a suitable star. But a longer focal length can make guiding more accurate.

[Anthonyexmouth]

1 minute ago, wimvb said:

Many imagers use a finder guider with the ed80, with good results. But if you plan to upgrade your scope to a longer fl at some point, an st80 for guide scope may be a better solution. With guiding equipment it's very much "if it ain't broke, ..."

The shorter fl of the guide scope makes it easier to find a suitable star. But a longer focal length can make guiding more accurate.

i'm finding the mounting for the 9x50 a bit of a pain to focus, its kinda wobbly with the o-ring and one set of adjustment screws. im not planning on going to a longer focal length at the moment. i do have my skymax 90 which i'd like to mount on top or along side the ED80 at some point but not quite ready to try long exposures on that. 

[wimvb]

The ed50 should be good enough for your current scope. I believe that the general rule is to have a guide pixel scale to be at most twice the imaging pixel scale. You just need to compare pixel size / fl for your imaging and guiding combination. I think that either one of your options should work. The st80 is a bit heavier and bulkier, but no problem for your mount. Imo, either one can give you good guiding.

[Marky1973]

Although I haven't been able to use it in anger yet, I have the 50mm Evoguide ready to go on my ED72 Scope and it is a very nice piece of kit. 

However, when I had my old ED80 I used an st80 on top with my 120mm and it worked a treat. You can get st80s second hand for around £70 so a lot cheaper than the Evoguide if budget is an issue. Bolt it down tight and you should have a problem. You will need an extension tube to focus with the zwo camera, but the Barlow that comes with the ST80 did the job well.

[Anthonyexmouth]

so have you swapped from an ed80 to an ed72?

 

[spillage]

I have two st80's that I use as guide scopes and find they do a great job. I use a steel bar and bolts to attach the st80 to the imaging scope to keep it nice and solid. 

[Anthonyexmouth]

i've got a spare long dovetail, am i right in thinking i can bolt this to the rings on my ED80 and the rings of a ST80 to it too.

[Marky1973]

Yep, that's exactly what I did! You might need to get creative with the bolts you use as I have always found the rationale between choosing size and thread pitches infuriatingly bizarre! ?

And yep, changed up (down?) from ED80 to ED72! Largely to get a lighter rig and a wider field of view....upgraded to a larger sensor camera as well.

[Anthonyexmouth]

I came close to getting the ED72 so i could use it with my HEQ5 at home and my SWSA when out and about. but a bargain ED80 came up on here a few weeks ago and couldnt resist. might still go for the ED72 at some point. 

[Marky1973]

The ED80 is a fantastic scope , you won't be disappointed with it....although it might be a bit heavy for the SWSA. been tempted with one of those mounts myself for travel, but need to save up a bit again! ?

[ollypenrice]

11 hours ago, spillage said:

I have two st80's that I use as guide scopes and find they do a great job. I use a steel bar and bolts to attach the st80 to the imaging scope to keep it nice and solid. 

So do I and one of them is guiding a 140mm refractor imaging at 0.9 arcseconds per pixel with no difficulty whatever. I make sure everything is tight and I used a lenseless Barlow body Araldited into the draw tube to hold the camera and get the backfocus. It must be at least three years since I did anything at all to this ST80 guidescope, including touching the focus - not that fine focus is a good thing in a guide system. (Source Craig Stark, author of PHD.)

I'm sure there are other alternatives but my pair of ST80s have been 'just doing it' for years.

Olly