Thinking of a change - imaging with a 4" refractor?

[Leebert]

After a while of chewing things over, I’m looking to take a change in direction.

Since I started in astronomy, I have been a mainly visual observer who has more recently dabbled in imaging.

I would now like to pursue with the imaging side of things more. To do this, I need to consolidate some of the OTAs I own (a modified 200p and a 9.25) and and set up an imaging rig. I plan to get a triplet refractor of around 4” to go with a 66 refractor that I already have as a guide scope mounted on an HEQ5 pro. I realise the HEQ5 isn’t the ideal mount but I have to do this one step at a time.

After seeing some impressive results from a friends Altair Astro 60mm triplet, I’m liking the look of the 102mm version. Does anyone have any experience with one of these scopes please? Alternatively, I’m open to suggestions to other makes / models in a similar budget (up to £1500).

Many thanks,

Lee

[johnrt]

What makes you think the HEQ5 is an unsuitable imaging mount? Quite the opposite I'd say! Is there any particular reason you are looking at a bigger aperture scope, the workhorse for most imagers is a quality 80mm triplet.

[ollypenrice]

What makes you think the HEQ5 is an unsuitable imaging mount? Quite the opposite I'd say! Is there any particular reason you are looking at a bigger aperture scope, the workhorse for most imagers is a quality 80mm triplet.

Agreed. WIth a 4 inch apo aboard the HEQ5 is likely to be no different from an NEQ6 and, given the variable QC, might perfectly well be better than a random NEQ6. (I have two NEQ sixes. Very good value, but no more accurate than the HEQ fives I've seen.)

Olly

[lensman57]

After a while of chewing things over, I’m looking to take a change in direction.

Since I started in astronomy, I have been a mainly visual observer who has more recently dabbled in imaging.

I would now like to pursue with the imaging side of things more. To do this, I need to consolidate some of the OTAs I own (a modified 200p and a 9.25) and and set up an imaging rig. I plan to get a triplet refractor of around 4” to go with a 66 refractor that I already have as a guide scope mounted on an HEQ5 pro. I realise the HEQ5 isn’t the ideal mount but I have to do this one step at a time.

After seeing some impressive results from a friends Altair Astro 60mm triplet, I’m liking the look of the 102mm version. Does anyone have any experience with one of these scopes please? Alternatively, I’m open to suggestions to other makes / models in a similar budget (up to £1500).

Many thanks,

Lee

Hi Lee,

I am only new to AP but I think that unless you wish to image with very large aperture super fasy NEWT Astro Graphs your mount is more than adequate. As you know most people choose an 80 mm ED scope for widefield imaging, some targets require larger aperture and perhaps more focal length for better image scale. I was advised to use a free piece of software call CCDCalc, it will show you what DSO objects look like in a particular scope and camera combination. I think you could use your 66 mm frac for imaging and convert your finderscope to a guide scope to begin with and see how you'd get on, this is the most economical way to start IMHO.

Your mount is more than capable of supporting two medium sized scopes side by side.

Regards,

A.G

[nmoushon]

There's nothing wrong with the mount you got. Will work just fine. The triplet 102mm would be a great imaging scope. Not sure what the f/ratio is but im guessing f6-7. Which isnt bad but you might want a reducer/flattener, which will add to your budget. Also making your FOV wider. If you want to do more wide field imaging than you got one of the better scopes in that budget. But if you are wanting longer FL than a Newt or even put a reducer on your 9.25 but both of those would more than likely require you to get a guide scope set up with it.

[ollypenrice]

The scope comes with a flattener, I think. All doublet and triplet systems need them on larger chips. Only four element systems manage without.

Olly

[Leebert]

Thanks for the reassurance on the mount. I had incorrectly thought that a 4" triplet with all the camera and guiding gear on board would be near the limit for reasonable imaging set up. The mount works well so it's good to know I can continue to use it for future plans.

The thought process behind it all is that I get frustrated that each different scope needing different adapters and the 2"filter that works a treat with the 200p doesn't fit anywhere in the imaging train on the 9.25 without yet another purchase etc. My theory is that if I reduced the amount of scopes I had and put together a single set-up than I would only need one set of adapters and filters to cover all eventualities. Less frustration - more images due to learning one set-up well rather than many different set ups a bit.

One thing I hadn't noticed is that the Altair Astro comes with the option of a flattener only and not a flattener/reducer. Would a FF/FR designed for an f7 system work with the scope?

I am open the other OTAs too but want to buy something that will stay with me. That was one reason for going for a 102mm over an 80mm to give me that little extra light gathering power.

Many thanks,

Lee

[ollypenrice]

Thanks for the reassurance on the mount. I had incorrectly thought that a 4" triplet with all the camera and guiding gear on board would be near the limit for reasonable imaging set up. The mount works well so it's good to know I can continue to use it for future plans.

The thought process behind it all is that I get frustrated that each different scope needing different adapters and the 2"filter that works a treat with the 200p doesn't fit anywhere in the imaging train on the 9.25 without yet another purchase etc. My theory is that if I reduced the amount of scopes I had and put together a single set-up than I would only need one set of adapters and filters to cover all eventualities. Less frustration - more images due to learning one set-up well rather than many different set ups a bit.

One thing I hadn't noticed is that the Altair Astro comes with the option of a flattener only and not a flattener/reducer. Would a FF/FR designed for an f7 system work with the scope?

I am open the other OTAs too but want to buy something that will stay with me. That was one reason for going for a 102mm over an 80mm to give me that little extra light gathering power.

Many thanks,

Lee

I doubt that anyone can say whether a reducer flattener would work without trying one on the scope. These things are hard to predict, no matter what the setup.

Olly

[Leebert]

Thanks Olly. I thought that would be the case.

Thanks too to Lensman57. I have drilled and tapped a bracket to mount a 9x50 skywatcher finder/guider onto the 66. I'll give it a go tonight. The moon doesn't set until gone 0300 so might go for an early Sunday morning session with M101.