Recommend my first actual AP scope

[Paul2019]

Hi all,

 

sorry if I have posted this in the wrong place. I find myself having a bit of a mare trying to chose my first AP scope.

Currently I’m having moderate success with my DSLR, 18-55 kit lens and 50mm prime on a star adventurer mini. 
 

My main interest is DSO imaging with an emphasis on galaxies and also nebulas of all types. This is where I get stuck, obviously for galaxies I need a long focal length and for nebulas I need something shortish. Is there a middle ground? 
 

In terms of mount I have decided on the eq6-r. I will be guiding but I’m undecided on what to get there too and hope to get an ASIAIR when they are available again too.

Im also reasonably confident I want to get a 2600mm too but I’m hoping to stick to the DSLR at the moment as mount etc is more important. 
 

scope budget is up to £1500 which makes it even harder I think. I would much prefer a refractor and have little interest in a reflector for this. That said I realise something like the EDGE 8 HD would likely be good for galaxies but rubbish for the bigger dso’s.

thanks for any help

 

paul

[vlaiv]

6 minutes ago, Paul2019 said:

That said I realise something like the EDGE 8 HD would likely be good for galaxies but rubbish for the bigger dso’s.

That depends on how you use it.

Since you have DSLR and plan on getting 2600 (or rather IMX571 in some shape and/or form), I'm going to assume following:

APS-C sized sensor and 3.76um pixel size.

You want middle ground, so both galaxies and nebulae - 1.8"/px is good place for that (and seeing conditions, and mount performance). Simple calculation gives us ~430mm of FL.

Here is scope + flattener for you:

https://www.teleskop-express.de/shop/product_info.php/info/p14015_TS-Optics-APO-Refractor-96-576-mm---FCD100-Triplet-Lens-from-Japan.html

+

https://www.teleskop-express.de/shop/product_info.php/info/p11122_Riccardi-0-75x-APO-Reducer-and-Flattener-with-M63x1-Thread.html

Not sure what is current exchange rate so it could be a tad over your budget.

 

[Paul2019]

59 minutes ago, vlaiv said:

That depends on how you use it.

Since you have DSLR and plan on getting 2600 (or rather IMX571 in some shape and/or form), I'm going to assume following:

APS-C sized sensor and 3.76um pixel size.

You want middle ground, so both galaxies and nebulae - 1.8"/px is good place for that (and seeing conditions, and mount performance). Simple calculation gives us ~430mm of FL.

Here is scope + flattener for you:

https://www.teleskop-express.de/shop/product_info.php/info/p14015_TS-Optics-APO-Refractor-96-576-mm---FCD100-Triplet-Lens-from-Japan.html

+

https://www.teleskop-express.de/shop/product_info.php/info/p11122_Riccardi-0-75x-APO-Reducer-and-Flattener-with-M63x1-Thread.html

Not sure what is current exchange rate so it could be a tad over your budget.

 

Thanks for the reply vlav. Do you think the triplet is the right way to go or should I consider a similar sized doublet and use the savings towards the camera? 

[vlaiv]

17 minutes ago, Paul2019 said:

Thanks for the reply vlav. Do you think the triplet is the right way to go or should I consider a similar sized doublet and use the savings towards the camera? 

Doublets do have some residual color and I would not recommend them for serious imaging.

If you don't mind having a bit more bloated stars in LRGB or some bluish halo here and there with OSC - then, sure, doublet can save some money, but for really tight stars - go with triplet.

[Paul2019]

Just now, vlaiv said:

Doublets do have some residual color and I would not recommend them for serious imaging.

If you don't mind having a bit more bloated stars in LRGB or some bluish halo here and there with OSC - then, sure, doublet can save some money, but for really tight stars - go with triplet.

Thanks for the advice, coming from yourself I’ll gladly take it. 
 

Looks like I should be buying my wife something nice 

[The Lazy Astronomer]

I'll add my personal experience, which will pretty much agree with vlaiv's advice: I use an Esprit100 (550mm FL) with a 294MM (4.63um pixels), which gives me an image scale of ~1.7"/px. My guiding is usually 0.5 - 0.7", and my measured FWHM usually leads me to bin my stacked image 2x2, so I'm already oversampling and l can't see any particular advantage to me to increase my focal length with my typical seeing conditions (making the assumption the sky is my biggest limiting factor in ability to resolve detail).

In short, based on my experience, I think you'll be quite happy with the above recommended image scale from vlaiv, and the FOV afforded by an APS-C sensor with 400 - 500mm of FL should be quite adequate for the majority of nebulae and the larger galaxies. Just be aware though that galaxies (excluding M31) will appear somewhat small in the full frame of the image, but you can always crop the image.