(DSLR+Scope+LP filter) or (mono+RGBHa+DSLR lens)?

[JayPea]

After a year dipping my toe in the AP waters I’m ready to upgrade. I started with second hand bits. I spent the bulk of my budget on a used HEQ5pro and that came with a Skywatcher  StarTravel  120 so I used that. It’s not the best optics for AP, stars around the edge have shapes that look like you’ve just hit warp drive and without the Baader contrast booster filter it came with the stars go mega blobby and blue.

The advice from the local Astronomy club was get your process sussed first and I think I’m happy there. I set up a DSLR on the scope and the guider is USB’d to an old laptop. By the time I’ve lugged it all out, pole aligned, focussed, taken flats and I’m plugged in and guiding an hour has easily passed. I set my intervalometer up and off I go. I’ll typically run for an up to an hour at a time and then go and check all is OK (I have been known to regularly leave the focus mask on..). I'm not keen to make things much more complicated or hassle than this.

 

So this is where I’m starting from:
- The above mount and scope plus I’ve already successfully added basic guiding
- I use unmodded Nikon DSLR’s (usually the 3.75um pixel size D7100 but I also have a 4.9um D800)
- I set up and take down every session at home and I’m mains powered. I can’t see me managing to go out to a dark site (don’t have a battery pack anyway).
- I’m very light polluted, unfortunately not just orange street lights and now lots of flashing Christmas lights about 3m away from my spot– I despair!
- I have tried the DSLR’s on my larger camera lenses (Nikon 70-200 2.8, and I have a x1.4TC and a Sigma Sport 150-600/F5-6.3). Images look OK to me but I think I struggle without a LP filter and they are £100’s to get one big enough for these front elements.

 

I’m now unsure what the next direction should be.  I swing between upgrading the scope with a proper LP filter and continue to use the DSLR. Or get a mono (+LRGB Ha) astrophotography camera on my Nikon lenses. I’m sure I’ll end up doing both in the fullness of time but I’m not sure I can do both (=spend all that money!) at the same time.

So if a new scope is first I was considering:

The £550 Skywatcher Equinox Pro 80ED (500mm 6.25) + a good LP filter + finder + guide scope mounting brackets £?? Does it need a flattener/reducer? Another £70+?
or the £600 Altair Astro 80ED-R 2016 (550mm f7) + a good LP filter + finder, field flattener/reducer to 448mm f5.6 £100
Budget looks like it has to be £700-£800 maybe a bit more depending on the LP filter (which filter? is it really worth it if I have mixed light pollution?).

 

Or a mono camera set up first?

I’m struggling to find anything that avoids me concluding I should just go to the  ZWO ASI16000 mono (uncooled £1000) and be done with it as it ticks all the boxes. That has a modest pixel (3.75um), decent sensor FOV/size and more MP, short optical path to help fitting a wheel between it and a Nikon lens. While there are others at less than half the price (e.g. ASI290MM) you compromise on smaller pixels, lower MP count, longer optical path (if critical for using with a Nikon lens?) and maybe I'd be itching to upgrade again too soon.
Then a filter wheel, filters + 7.5nm Ha and adapters (£250 for basic ZWO manual set, >£450 for motorised and parfocal). Adapters to fit a Nikon look around £50 (Nikon G to EOS then EOS to Filter wheel?).

I’ve heard everything from I’ll be refocusing during the night even with parfocals due to the cold (so might as well go basic and manual?) and you don’t if you do luminance first and RGB after where focus is less critical if it drifts or is binned. The latter is for higher megapixel sensor and the former for lower pixel counts? Would I probably have to refocus a lot with a camera lens anyway?

Costs: Smaller camera (£400) or bigger camera (£1000), basic filter system (£250) up to auto parfocal system (>£450). + costs of mounting brackets to twin with the guider as I couldn’t piggy back like I currently do. These rings, adapters and brackets can really add up.

 

So is it a mono camera system first? It will help most with my light polluted home environment and improve over my current optics but I’d be using camera lenses (might be nice for the new range of FoV’s). Or is it a better scope and better LP filter with my existing DSLR?

 

So I was after some advice. Scope or mono camera first? and what might be a good future proof set up? Anyone here stuck a ASI1600 and basic filter wheel kit on a Nikon lens (that would cost me £1000 + £250)? I’m think this might give me the biggest improvement from what I have out of the two options. It's a shame it's the most expensive.

 

I'd be most interested to hear about  mono + filter wheel systems on DSLR lenses, particularly Nikon glass. Is it worth the effort?

 

Thanks, John

[D4N]

Ok so your problems are:

Unmodded DSLR's for camera - not sensitive to Ha.

Non apo scope - CA and colour bloating.

Light Pollution.

 

Getting a new scope would only fix one of those problems, getting a new camera could fix all 3.  You would also need the flattener to get rid of the warp effects.

There isn't much focus travel on a lens so you need to get the spacing right and fit whatever filters you want in there too.  You can get lense adaptors that can fit a filter internally but that would mean removing the lens to change filters.

Zoom lenses aren't ideal for Astro work, do you have any prime lenses?

[JayPea]

D4N, thanks for the respose. I think that's where I've got to as well. I think the ASI1600 will work OK with filter wheel and nikon lenses as i see specific adapters for it. Any other cameras and I'm not sure I'll get the spacing right.

The two nikon zooms are the longest i have. My primes are only up to 90mm. Assuming zoom slipping (the sigma locks) is manageable I know they are sharp. Are there other issues with zooms?

[D4N]

I think extra glass isn't always a good thing, it is more reflections and absorbtion of the photons you want to make it to the sensor.

I could check out the spacing on my asi178mc as that has a DSLR lens on it and I imagine it it much the same as the 1600 for front flange arrangement.  I definately have a spacer in there, I just can't remember how big it is.

The 90mm prime would be quite wide with the asi1600, 11.25°x8.5° of sky on the chip so the likes of heart and soul would fit on with space to spare.

I built a cooler for my asi178mc, it seems pretty effective and massively reduces the noise.  A lot cheaper than buying the cooled version of the camera too