Atmospheric dispersion corrector: Omegon v. ZWO

[Stub Mandrel]

On 29/01/2018 at 01:21, Merlin66 said:

Atmospheric dispersion is a real issue in spectroscopy!!! The entrance slit has to be orientated to collect all the spectral data....

 

Presumably rotating the slit is all it takes, so you don't need and ADC.

[timwetherell]

7 hours ago, Louis D said:

How much in-focus is required for visual use of these ADCs?

With my 1250mm fl scope about 2" or 50mm - pretty much the physical length of the ADC  

[Paul73]

Fascinating thread.

I had virtually written off planetary observing for this year. Buying a season’s observing for £130 seems like the bargain of the century!!!

Paul

[Relpet]

1 hour ago, Paul73 said:

Fascinating thread.

I had virtually written off planetary observing for this year. Buying a season’s observing for £130 seems like the bargain of the century!!!

Paul

I'm really pleased to have started this thread as it has produced a lot of informed comment.  If anyone is interested in the Omegon it can be had from Astroshopurania in Belgium for 129 euros plus modest delivery.  I don't know of a UK dealer.  I like the red marking ring on the Omegon but other than that can't see any difference between it and the ZWO.

[Knighty2112]

Uh oh! I think my next purchase is going to be an ADC for the upcoming Mars and Jupiter oppositions later this year. FLO has the ZWO ADC up for £107, so if it works as good as I’ve been reading about it’ll be well worth it! Roll on pay day!  

[Knighty2112]

On 01/02/2018 at 09:31, timwetherell said:

Mine's a ZWO brand that I got from First Light Optics and I'm 100% happy with it and their service. The disadvantage of the cheaper designs (like ZWO) is that the image shifts a bit as you adjust the prisms but that's something I can live with given the very reasonable price. The total range of motion is only about 20 minutes of arc so it's not really an issue. And of course once adjusted for a given elevation, it stays very much the same from night to night. Now I just pop it in each morning observing jupiter - Other than rotating the whole thing to minimise the dispersion, no other messing about is usually required. I did this sketch this morning with my 7" refractor (Jupiter on the meridian and about 20° elevation) LHS with the ADC - beautiful view of the red spot  RHS without the ADC - can just about make out the equatorial bands. Of course it won't correct for the worse seeing associated with low elevation but I'd say it makes more difference than just about any other eyepiecey/filtery thing I've ever bought!

Flabbergasted at the difference with and without the ADC! Excellent drawings too Sir!  

[Stub Mandrel]

FWIW this is the effect atmospheric dispersion has on imaging planets:

I got round this by replacing green (worst affected) with a mix of red and blue:

But this year I will have a secret weapon from FLO

 

[Knighty2112]

19 minutes ago, Stub Mandrel said:

FWIW this is the effect atmospheric dispersion has on imaging planets:

I got round this by replacing green (worst affected) with a mix of red and blue:

But this year I will have a secret weapon from FLO

 

Good to know. I plan on using my new ZWO ASI 120 MC camera on some planets soon, so hoping that will make a difference here too along with visual observations. 

[Relpet]

1 hour ago, Knighty2112 said:

Uh oh! I think my next purchase is going to be an ADC for the upcoming Mars and Jupiter oppositions later this year. FLO has the ZWO ADC up for £107, so if it works as good as I’ve been reading about it’ll be well worth it! Roll on pay day!  

That's good to know.  I'd rather support the sponsor whenever possible and it's those oppositions, low in the sky, that spurred me to start the thread.

[johngm]

I was fortunate to be working in the states before Christmas, so I managed to pick up the ZWO version for around 80 quid 

John

[Paul73]

For imaging, you can realign the different wavelengths during the processing stage. Not sure which would do a better job.

Paul

[Stub Mandrel]

2 minutes ago, Paul73 said:

For imaging, you can realign the different wavelengths during the processing stage. Not sure which would do a better job.

Paul

To an extent, but as each of RG and B is really a range of wavelengths you still get blurring.

In my images above you can see the green in particular, is heavily blurred, the inset colour images is the three channels aligned and the result is, frankly, poor.

I'm getting a deep red filter which will be more tolerant of poor seeing and less blurred as it is relatively narrowband (especially when used with IR blocking), but even so an ADC should make all colour channels sharper.

[Paul73]

2 hours ago, Knighty2112 said:

Good to know. I plan on using my new ZWO ASI 120 MC camera on some planets soon, so hoping that will make a difference here too along with visual observations. 

Sounds familiar. My ZWO ASI120 MM is awaiting planetary first light too.

As you say; roll on payday!

Paul

[FLO]

On 20/02/2018 at 00:00, Relpet said:

If anyone is interested in the Omegon it can be had from Astroshopurania in Belgium for 129 euros plus modest delivery.  I don't know of a UK dealer.  

As someone mentioned earlier, 'Omegon' is Astroshop's own brand label so it is unlikely you will find a stockist here in the UK but the original ZWO ADC has been available in the UK (at several retailers) for some time, since early 2016. 

Interestingly, it also costs less here in the UK. 

 

[Mark at Beaufort]

I must admit I was not aware of an ADC. I looked at the manual and noted that you can use a Newtonian - i don't own a refractor anymore. I would certainly be interested if anyone has used an ADC on a Newt and what was the result.

[Stub Mandrel]

1 hour ago, FLO said:

the original ZWO ADC has been available in the UK (at several retailers) for some time, since early 2016. 

Interestingly, it also costs less here in the UK. 

I noticed!

[Louis D]

1 hour ago, Mark at Beaufort said:

I must admit I was not aware of an ADC. I looked at the manual and noted that you can use a Newtonian - i don't own a refractor anymore. I would certainly be interested if anyone has used an ADC on a Newt and what was the result.

Only if you have 50mm or more of in-focus or plan on using a barlow to get more in-focus.  I suppose a Newt designed for astrophotography like the 130PDS would have no problems with the focuser extension removed.

[Knighty2112]

2 hours ago, FLO said:

As someone mentioned earlier, 'Omegon' is Astroshop's own brand label so it is unlikely you will find a stockist here in the UK but the original ZWO ADC has been available in the UK (at several retailers) for some time, since early 2016. 

Interestingly, it also costs less here in the UK. 

 

Payday in approx 6 days, so can you make sure you have some in stock on the day I do get paid please! Hehe!  

[Stub Mandrel]

While I can probably figure it out (more or less) are there any instructions for the ZWO ADC?

For example, I assume correct orientation is with the levers equally spaced either side of down (or perhaps up?)

Is there a way to estimate the correct position of the levers from the object's ALT?

<edit> I found this:

ADC Manual EN.pdf