11 replies to this topic

[danishastrophotographer]

I have for a year now been imaging with the I optron skyguider pro, a lens, and a dslr. The rusults I have made has been acceptable, but I would like to step-up the game even further.

 

My plan is to buy a the ZWO ASI183mm pro, combine it with a SkyWatcher EQ5 GoTo, and the Sigam 150-600mm. I know that getting into both a new mount, a ccd camera and software is going to be frustating and take time, but I am prepared for that. I was then going for only narrow band imaging, and I already have Ha and o3 filter, though a clip-in model, but i assume you could get drawers in the optical train that could do the job?

 

My goals are to only image nebulaes and get somewhat high resolution images with nice colors and get a sense of depth in the nebula. But would the this even make sense to buy, or am I way of track?

[idclimber]

I would suggest planning even further ahead. Assuming you maintain interest in this endeavor you will end up with one if not two dedicated scopes for imaging. The reason is simple, focusing the terrestrial lens all by itself will be a chore you will not want to live with long. You will also quickly realize these lenses are less than sharp for this purpose and quickly show their flaws. Also the best SLR lenses are manual ones and not zooms. 

 

The question then is, does the EQ5 have enough stability for those theoretical scopes. I have no expertise with that mount myself but I do hear experienced posters here say it is not suitable for the larger scopes and often suggest the EQ6-R pro for that reason.

 

The most important and limiting component for AP is the mount. 

[Tapio]

Zoom lenses are generally not the best choice for astro imaging.

I think a refractor say 60-80mm would be better.

Easier to deal with focusing and guiding etc.

[RedLionNJ]

I'm not hearing anything about an autoguiding capability.  At 600mm (assuming everything else is ok), you're going to need autoguiding. The EQ5 itself will not track sufficiently, no matter how well polar-aligned.

 

You should also (as mentioned above) verify you can get tack-sharp images with that lens at the desired focal length.

[dhaval]

Unless you already have a Sigma 150-600mm lens, I would suggest you think of getting a small refractor. I am not sure if I have seen a lens that is suitable for AP (SharpStar seems to be making one though - their AKSAR 400mm series seems nice). But quite honestly, a RedCat scope would be a much better bet - they are well corrected for AP.

 

CS!

[danishastrophotographer]

I have looked at some telscopes, and found a guy who sells the skywatcher 80mm f/7.5 ed refractor both with a reducer and the fieldflattener. Would this make more sense? 

 

With a focal lenght of 600mm that would give me a image scale of 0.82 wich isn't the end of the world right?

 

One of the comments also said that at 600mm it would probably not be as sharp tracking, but only weighing 2.5 kg, is that really going to be a problem when the max. payload capacity is stated at 10kg?

[Tapio]

Yes ed80 with a reducer makes more sense.

Of tracking accuracy - the weight isn't the problem. It's the mechanical imperfections of the lower end mounts which means you need autoguiding when the focal length exceeds certain number, and 600 mm certainly exceeds it.

[fewayne]

The ZWO mono cameras come with a disk, looks like a big washer, that threads inside the camera's adapter ring. The center hole is 1.25" and is threaded for that size filter. So if you're doing one band per night, you can just assemble the imaging train with that filter and go for it. Dunno what size your existing ones are, but filter drawers are a thing that one can obtain.

 

You might also look into manual filter wheels, much more convenient than a drawer and still quite inexpensive -- if you check the CN classifieds they usually go for under a hundred bucks, sometimes with filters included.

 

Older fixed-focal-length telephotos of very good optical quality are out there for not a ton of money too. "Nobody" wants a manual-everything prime these days, which keeps the prices in line. One big reason I went with Pentax for my DSLRs, but other brands work too. 200-400mm is a good compromise between image scale, price, and reasonable ease of use on a lower-end mount.

But what I'd counsel you to do is put off spending big bucks on glass and go wild on a mount. A higher-end mount is the same difficulty to use as a low-end one, but enormously less difficult to pull off decent images, especially early in your career. There are a ton of targets you can image at 200-400mm with a good mount. If you want to do narrowband, that advice goes double, since exposure times are of necessity much longer, magnifying any mount issues. I adore my Stellarvue to death, but really wish I'd put that thousand dollars into a better mount and picked up an old Pentax telephoto to use for a year.

[Stelios]

I have looked at some telscopes, and found a guy who sells the skywatcher 80mm f/7.5 ed refractor both with a reducer and the fieldflattener. Would this make more sense? 

 

With a focal lenght of 600mm that would give me a image scale of 0.82 wich isn't the end of the world right?

 

One of the comments also said that at 600mm it would probably not be as sharp tracking, but only weighing 2.5 kg, is that really going to be a problem when the max. payload capacity is stated at 10kg?

The full imaging train will weigh more than 2.5 kg. The maximum payload of 10kg is for visual, not AP. You would need to guide at 600mm *even if your imaging load was zero*. 

 

If you are trying to up your game, don't be bogged down with the EQ5. Go at least for a HEQ5. Postpone the other upgrades if you need to. Rome wasn't built in a day, and *NOTHING* is more important than the mount. 

 

As others already said, you are usually better off with a scope than a zoom lens.

[danishastrophotographer]

I have thought about what you guys have said, and It have come down to this:

 

- EQ6 synscan

- SkyWatcher 80mm ed

- Either qhy183 or asi1600mm

 

If theres any money left i will invest in some autoguiding. Does this sound reasonable?

[pedxing]

You are going to have to autoguide from the get-go, so you may as well put that in your budget/plan up front.

[idclimber]

I would second the need for a guider. Assuming you already have a DSLR and mentioned Sigma lens and your budget is not unlimited,  I would go in this order:

 

Mount

Guider/guide camera

80mm Refractor

Cooled camera. 

 

I believe there are two 80mm SW scopes, a doublet and a triplet. If you want specific feedback I would specify which one you are considering.