Which refractor for Quark

[SAW]

Hi,

I am looking for a refractor to use with a Quark and a 178MM or maybe a 174MM. I would like something that's quite light as it's going on a Vixen AP SM mount which is rated at 6kg max. I may also use it for some lunar observing and imaging with the same camera(s). Not sure if I should go for a doublet or triplet ? Or get a triplet that I can also use for DSO imaging. I've looked at the StellaMira 85mm ED2 Triplet f/6.6, SharpStar 94EDPH f/5.5 Triplet and Takahashi 76DCU. The first two are probably on the limit for the mount but does give me the option for DSO imaging on another mount. I've also looked at the Altair Starwave 80ED-R ED Doublet.

Thanks.

[Peter Drew]

On paper, the StellaMira 85 would be a good choice as the fr 6.6 coupled with the Quark's 4.2x Barlow gives the optimum overall focal ratio for the Quark system.     🙂

[Steve Clay]

I use a Ed80 with quark on a solarquest mount.  Along-with a vixen NPL 30 eyepiece or the svbony 10-30 zoom. Works great.

[bomberbaz]

3 hours ago, Steve Clay said:

I use a Ed80 with quark on a solarquest mount.  Along-with a vixen NPL 30 eyepiece or the svbony 10-30 zoom. Works great.

If you use a 0.85 SW reducer it gives you a F.6.4 which as peter says above drops into the quark sweet spot. 

[Luke]

I didn't image with it, but I'd consider the Skywatcher ED100. It performs great with the Quark visually and is a really good scope. Quite long but light. The focal length should be fine with the ASI 174 and a cheap 0.5x reducer on the camera nose. I used the ASI174 with the ED120, which has the same 900mm focal length.

Probably not the best choice for DSO imaging, but great visually with the Quark, and for white light too. I find the 100mm aperture helps for closer up detail over my Tele Vue 85 and for me is a sweet spot between scope size and weight to close up detail.

If I kept one frac only, it might be the ED100! Good luck deciding.

 

 

Edited April 8, 2021 by Luke

[skybadger]

Just be aware that you probably need either an ERF or other pre-filter to protect the quark as you go above 80mm. Mine self-heats on the 80mm even with an IR cut  pre-filter which takes me off band. 

 

[Nigella Bryant]

You'd definitely need an erf if over 80mm. On the plus side you don't need expensive ed or triplet scopes. Achromatic scopes are fine. I use achromatic scopes albeit for cak.  Essentially you're observing/imaging in one wave length and mono. I've used a cheap £100 pound 70mm achromatic for solar and have recently bought a cheap 100mm achromatic. I use an 80ed for White light with Hershel wedge. 

Edited April 8, 2021 by Nigella Bryant

[Peter Drew]

There is a caveat with this otherwise sound advice.  I's true that working on Ha is a monochromatic wavelength so no need for an apochromatic class telescope.  However, chromatic aberration isn't the only limitation of inexpensive refractors, spherical aberration and so-so figuring also conspire to provide less than perfect images.  So if contemplating an achromat, make sure it's a good one.        🙂

[bomberbaz]

3 hours ago, Nigella Bryant said:

You'd definitely need an erf if over 80mm. On the plus side you don't need expensive ed or triplet scopes. Achromatic scopes are fine. I use achromatic scopes albeit for cak.  Essentially you're observing/imaging in one wave length and mono. I've used a cheap £100 pound 70mm achromatic for solar and have recently bought a cheap 100mm achromatic. I use an 80ed for White light with Hershel wedge. 

Do you find you get any granulation on white light with just the 80mm Nigella.  I currently use a Bressier 102L F9.8 and thus far have not overly very impressed with results.

[Steve Clay]

4 hours ago, skybadger said:

Just be aware that you probably need either an ERF or other pre-filter to protect the quark as you go above 80mm. Mine self-heats on the 80mm even with an IR cut  pre-filter which takes me off band. 

 

I use a baader 2inch 35nm Ha filter about 3 inches ahead of the 1.25 inch diagonal. I use 2 baader fine tune rings to achieve this.

[Nigella Bryant]

1 hour ago, bomberbaz said:

Do you find you get any granulation on white light with just the 80mm Nigella.  I currently use a Bressier 102L F9.8 and thus far have not overly very impressed with results.

I use a badder cak filter which is really white light and granulation is easy to see but it's only used for imaging. To broad a band range for calcium k line. 

[bomberbaz]

32 minutes ago, Nigella Bryant said:

I use a badder cak filter which is really white light and granulation is easy to see but it's only used for imaging. To broad a band range for calcium k line. 

Ahh I was refering to visual, thanks for the reply anyway

[Nigella Bryant]

8 minutes ago, bomberbaz said:

Ahh I was refering to visual, thanks for the reply anyway

This is what I'm seeing using the zwo camera.

[bomberbaz]

38 minutes ago, Nigella Bryant said:

This is what I'm seeing using the zwo camera.

Very nice indeed Nigella. Think I need to restart my approach to WL solar afresh.

 

[skybadger]

16 hours ago, Steve Clay said:

I use a baader 2inch 35nm Ha filter about 3 inches ahead of the 1.25 inch diagonal. I use 2 baader fine tune rings to achieve this.

I tried that but found it fuzzed the image . I'll try. It again 

[Luke]

I had no joy with the Baader Ha filter and Quark! My Quark was way off band with it for some reason and I had to return the filter. I use a UV/IR cut (my one is Astronomik L-Filter UV-IR Block Typ 2c) up to 120mm. I've not had any problems with the UV/IR cut, with several Quarks in four different scopes. Hope you find a solution skybadger.

Edited April 9, 2021 by Luke

[Davey-T]

I think the recommendation for some sort of ERF is based on the worst case scenario probably for folks living in Arizona and similar geographic regions, I use the Baader 35nm ha filter in a 152mm refractor having previously used a UV/IR cut but prior to that used the Quark in 100mm refractor sans filter with no ill effects.

Dave

[Luke]

2 hours ago, Davey-T said:

I think the recommendation for some sort of ERF is based on the worst case scenario probably for folks living in Arizona and similar geographic regions, I use the Baader 35nm ha filter in a 152mm refractor having previously used a UV/IR cut but prior to that used the Quark in 100mm refractor sans filter with no ill effects.

Dave

Dave, can I ask, did you use the UV/IR cut in the 152mm as well, and was the Quark tuning the same / similar as when using the 35nm?

I'm curious why I had problems with the Baader 35nm H-a filter! The view was similar to when the Quark is warming up -  more like white light, and I tried the other tunings but they made little difference.

I gather the 35nm should block even better / light passing through should be cooler. So if the Quark was getting more heat from the UV/IR cut in my 120mm scope, that might explain different tuning.

But then I used the same tuning for that Quark in all my scopes including my little 60mm , which I presume would not generate that much heat. So if heat was affecting the tuning in the 120mm, then wouldn't the Quark have needed different tuning in the 60mm?

 I also used a UV/IR cut with the 60mm, just to be extra cautious!

After trying the 35nm I switched to my usual UV/IR cut and things were fine again, i.e. the only difference was the filter.

[Stu]

On 08/04/2021 at 19:37, Peter Drew said:

However, chromatic aberration isn't the only limitation of inexpensive refractors, spherical aberration and so-so figuring also conspire to provide less than perfect images.  So if contemplating an achromat, make sure it's a good one. 

Completely agree with this. There is much talk about not worrying about using an apo for Ha or even for white light if you are using a continuum filter. As Peter says, that’s fine, so long as the achro you use has a good figure and performance in terms of spherical aberration. SA can tend to kill off the fine detail that really pops out at high powers with a good apo.

On 08/04/2021 at 20:13, bomberbaz said:

Do you find you get any granulation on white light with just the 80mm Nigella.  I currently use a Bressier 102L F9.8 and thus far have not overly very impressed with results.

I’ve found 100mm to be quite a sweet spot for white light solar observing. It has enough aperture to give excellent detail whilst being perhaps less affected by seeing conditions than larger scopes, although obviously the best high power views come with excellent seeing. I would have thought the Bresser would perform reasonably well. What have the seeing conditions been like for you?

With my FC100DC it is rare that I don’t see clear granulation, and at times it can be quite startlingly sharp.

[Stu]

On 08/04/2021 at 15:57, Luke said:

I didn't image with it, but I'd consider the Skywatcher ED100. It performs great with the Quark visually and is a really good scope. Quite long but light. The focal length should be fine with the ASI 174 and a cheap 0.5x reducer on the camera nose. I used the ASI174 with the ED120, which has the same 900mm focal length.

Probably not the best choice for DSO imaging, but great visually with the Quark, and for white light too. I find the 100mm aperture helps for closer up detail over my Tele Vue 85 and for me is a sweet spot between scope size and weight to close up detail.

If I kept one frac only, it might be the ED100! Good luck deciding.

 

 

That’s interesting Luke. I would have thought the 100ED may be a bit slow and long focal length for best performance with a Quark but clearly not from your experience. The problem is often keeping the magnification down to match the seeing conditions isn’t it? I had good results with a TV85 and also a 106mm f6.5 triplet.

[Davey-T]

1 hour ago, Luke said:

Dave, can I ask, did you use the UV/IR cut in the 152mm as well, and was the Quark tuning the same / similar as when using the 35nm?

I'm curious why I had problems with the Baader 35nm H-a filter! The view was similar to when the Quark is warming up -  more like white light, and I tried the other tunings but they made little difference.

Hi Luke, yes used the UV/IR cut filter in the 152mm before I bought the Baader 35nm ha filter, a few years ago now but don't recall any alteration in the view or tuning.

Having now had several different Quarks and having two ATM I can vouch for the fact that none of them have ever been the same, I sent one to Ewan to compare to his and he confirmed they were as different as chalk and cheese.

The two I have at present produce similar views but imaging requires different settings in Firecapture, not done any particularly scientific analysis of this it just seems one lets through more light at the same settings.

Dave

[SAW]

I keep looking at the Tak 76DCU and 100DC. I've owned a 60Q but I want something with more aperture. Do you think a Tak 76 or 100 is going to be overkill for the Quark ? I'll use the scope for lunar as well. As it's going on a Vixen AP SM mount I have to be careful with weight it will only hold 6kg max so I want to be at 4kg at the most.

The 76DCU with Quark fut the ratio at around 30 and with the 100DC it around 31 so both ideal with the Quark.

[Stu]

1 hour ago, SAW said:

I keep looking at the Tak 76DCU and 100DC. I've owned a 60Q but I want something with more aperture. Do you think a Tak 76 or 100 is going to be overkill for the Quark ? I'll use the scope for lunar as well. As it's going on a Vixen AP SM mount I have to be careful with weight it will only hold 6kg max so I want to be at 4kg at the most.

The 76DCU with Quark fut the ratio at around 30 and with the 100DC it around 31 so both ideal with the Quark.

Depends on how important portability is to you. The 100 will be fantastic on the Moon, and the additional resolution will also benefit Quark views. White light solar observing with a Herschel wedge is also pretty amazing with a FC100. If portability is important the the 76 will still be worthwhile. I used to have both an FS60 and an FC76DC, the 60 gave excellent full disk views with a Quark, and the 76 obviously gives higher power views but not full disk.

[SAW]

I think I've ruled out the FS60 as I have a Vixem FL55ss so it's too similar in terms of FOV etc. 

[Stu]

27 minutes ago, SAW said:

I think I've ruled out the FS60 as I have a Vixem FL55ss so it's too similar in terms of FOV etc. 

Makes sense, although what I was meaning is that if you get the split tube FC76DC, then you can opt for either the FS60 or the FC76 objective and effectively have two scopes in one.