100-120mm decent refractor for solar use

[kirkster501]

Thinking of getting a Quark Chromosphere. Any suggestions for a refractor to use with it please folks?  Intend to additionally maybe use it for guiding and maybe also AP for slightly wider angle than my TEC 140 so something decent and not as cheap-as-chips.

Or should I buy an ERF and use my TEC140?

 

[Steve Clay]

I use an ED 80 with the chromosphere on a solarquest mount with 1.75 steel legs. Works an absolute treat. 

[Stu]

Don’t forget (I’m sure you haven’t) that the Quark has a built in x4.2 barlow, so your effective focal length becomes 4116mm in the TEC. This limits you to high power views (x128 with a 32mm plossl for example) which is fantastic if the seeing can take it, but too much if it won’t.

Smaller fracs with shorter focal lengths (around 400 to 500mm say) have the benefit of being able to offer full disk views.

f7 to f7.5 is an ideal focal ratio if I recall correctly, so the TEC is fine from that perspective but I do think something around the 100 f7 mark would probably be a better compromise given UK seeing conditions. That would put you at 2940mm effective focal length and x91 with a 32mm plossl.

[kirkster501]

... and I sold my lovely ED80 last year 🙈

Alright chaps, many thanks!

[vlaiv]

I've heard good things about this one:

https://www.teleskop-express.de/shop/product_info.php/info/p3041_TS-Optics-PHOTOLINE-115-mm-f-7-Triplet-Apo---2-5--RAP-focuser.html

Also, maybe consider use of Quark Combo instead of regular quark if you intend to do imaging alongside visual.

With Quark Combo, you'll be able to do close up shots / viewing but also full disk viewing.

Trick is to use both aperture masks and telecentric barlows. You can get x2 and x3 telecentrics from ES - they are supposed to be good, and simple aperture mask can help make scope be F/20 or F/30.

You can get full disk viewing with up to 1800mm focal length. This means that you need something like 400-450mm FL scope with regular quark to get full disk viewing.

Above scope is 800mm FL so you would not be able to get full disk with regular quark, but take x2 telecentric lens and make 80mm aperture mask. 1600mm FL and 80mm aperture - gives you F/20 system and full disk viewing with something like x120 magnification with ease.

Want to get very close in? Put x3 telecentric and you are at F/21 with 115mm of aperture. x200 mag should be doable without too much trouble.

BTW, put Riccardi FF/FR on above scope and you'll have 115mm aperture F/5.2 600mm FL wide field instrument for imaging.

[Macavity]

The ED80 objective certainly works well in by Solar Frankenscope.
I have always liked the look of these TS refractors! F/7 is ideal for
an even bigger Frankenscope. But then I'd need a bigger Baader
ERF filter etc., so perhaps not just for the moment... 😛

[kirkster501]

Thanks guys.

I don't fancy forking out £1000+ for an ERF for my TEC only to find its long FL means opportunities are limited.  I have only done white light with the TEC and want to start modestly with Ha.

So if I went for another 80mm or maybe a 100mm frac (preferably), I wouldn't  need an ERF and could just use the Quark on its own?  I read about the IR cut at the front of the diagonal.  Is this just a standard IR cut like a Baader that could be similarly used at night time?  Why wouldn't that shatter?

 

[Owmuchonomy]

An ED80 was a good option with my Quark.  Don't forget, any bigger aperture and its likely you will need at least an IR block on the diagonal (2").

[Stu]

12 minutes ago, kirkster501 said:

Thanks guys.

I don't fancy forking out £1000+ for an ERF for my TEC only to find its long FL means opportunities are limited.  I have only done white light with the TEC and want to start modestly with Ha.

So if I went for another 80mm or maybe a 100mm frac (preferably), I wouldn't  need an ERF and could just use the Quark on its own?  I read about the IR cut at the front of the diagonal.  Is this just a standard IR cut like a Baader that could be similarly used at night time?  Why wouldn't that shatter?

 

@Davey-T can possibly advise better on this, but I think the Baader 35nm H alpha filter will do the job with a 100mm scope (and likely larger I think), effectively a mini ERF.

https://www.baader-planetarium.com/en/baader-h-alpha-35nm-ccd-filter.html

[Steve Clay]

I went with the 35nm ha 2inch filter with my ED80 even though not strictly necessary. I did this A. To protect the quark and also to give me the option to use the ED120. I also moved the filter further forward by using baader 28mm fine tuning rings. I've tracked the sun for 5 hours and nothing got even slightly warm. 

[kirkster501]

Really?     This flimsy filter is taking the full focused light and heat from the objective.......  I'm amazed the glass doesn't crack or fracture....????

[Steve Clay]

25 minutes ago, kirkster501 said:

Really?     This flimsy filter is taking the full focused light and heat from the objective.......  I'm amazed the glass doesn't crack or fracture....????

This is all based on advice from daystar, here and solarchat forum. I'd researched the options on Ha for quite a while. The light is not focused when it hits the 35nm Ha filter. This first filter rejects all the energy back up the tube except the ha band. Hence it's reportedly better than just a UV/IR cut. I'm by no means an expert. However, it's all working fine giving great views.

[Peter Drew]

The 35nm Baader filter is of the reflection type rather than absorption so doesn't get particularly hot.    🙂

[Starflyer]

Following as I was about to ask the very same question.

[kirkster501]

Thanks guys.

Just to clarify for a numpty like me...  🤣  So, for appertures up to about 120mm-ish no need for an ERF up front at the objective and the Quark is fine at the focus point but you need to put in one of these UV-IR cut filters in front of it?  These are not the same as the night time UV/IR cuts filters?  I have one of those already.

For larger apertures you should use an ERF to drop the heat and energy coming down the tube?

I like the idea of the quark because it gives me future options with my TEC as well as another more modest 100-120 mm refractor I'll get.  At some point I might get an 80mm Lunt as well.

[Solar B]

The regular UV/IRs imho are not adequate as an ERF , the 35nm Baaders are actually 

mini D-ERFs so are more than adequate right up to 150mm in my experience.

However if your not used to Solar HA then I wouldn't recommend a Quark as your first 

foray as they can be very hard work given the mags your dealing with , EP selection 

is critical and they often do not make for relaxing views , thus many give up 

upon them.

I'd opt for a regular air spaced scope to begin with and see how you get on with that first.

Brian 

 

 

 

[Zakalwe]

16 minutes ago, Solar B said:

The regular UV/IRs imho are not adequate as an ERF , the 35nm Baaders are actually 

mini D-ERFs so are more than adequate right up to 150mm in my experience.

However if your not used to Solar HA then I wouldn't recommend a Quark as your first 

foray as they can be very hard work given the mags your dealing with , EP selection 

is critical and they often do not make for relaxing views , thus many give up 

upon them.

I'd opt for a regular air spaced scope to begin with and see how you get on with that first.

Brian 

 

 

 

All of the above.

The UV/IR filters pass a lot of heat through them, whereas the H-a filter blocks the vast majority of it.

Quarks aren't the easiest to start with, though once you get used to them (and you get a good one) then they are capable of producing an outstanding image. However, if you have zero H-a experience then I would think that a Quark could make for a very frustrating time.  You'll need good seeing to get the best out of them too.

The other thing to consider s what do you want to image? Full discs are a complete PITA with a Quark as you are into multi-pane mosaics.

 

[Zakalwe]

The TED is an oil-spaced scope, isn't it? If so, then I'd be very wary of using that for solar work unless it had a front ERF. I'm sure that Daystar used to specifically advise against using an oil-dpaced refractor or a Petzval design unless fitted with a front mounted ERF.

A 12060mm Baader D-ERF is another £900 plus the cost of a mounting cell.

[Rusted]

I use a full aperture 160mm Baader DERF + the 35nm Baader + a Beloptik KG3 in my 150/10 H-a PST mod.
Why? Because I might cook my expensive ZWO '174 camera with a sub-diameter ERF.

I cooked my ASI120 using a 90mm Baader D-ERF well inside focus of a 150/8 PST mod. After the PST etalon, ITF + BF5!
A hot beam continued after the 90mm internal D-ERF! Hot enough to remove my hand rather quickly at the open focuser.

Despite my extra filtration, my ASI174 soon reaches 40C on the SharpCap thermometer.
48C after a couple of hours of tracking the sun in summer. [Sun willing.]

An abundance of caution is desirable if you want to do visual with a larger aperture like your 140.
Why not explore a PST mod?  Stunning views in H-a both visually, binoviewing and for imaging.
Though you still have to afford the bigger D-ERF if you want to be safe. IMHO.

[kirkster501]

3 hours ago, Zakalwe said:

The TED is an oil-spaced scope, isn't it? If so, then I'd be very wary of using that for solar work unless it had a front ERF. I'm sure that Daystar used to specifically advise against using an oil-dpaced refractor or a Petzval design unless fitted with a front mounted ERF.

A 12060mm Baader D-ERF is another £900 plus the cost of a mounting cell.

I'm not using the TEC for the Quark, certainly not yet, and when/if I do I would buy an ERF.  However, to address your point the TEC is completely fine for white light solar and a Herschel Wedge.  Done so many times with Yuri's - the manufacturers - blessing.  He says, and I agree (FWIW) that the objective is just like a piece of glass on the table.  It is only when the rays come to focus when all the fireworks start.  Yuri says he has folks using his TEC200s perfectly fine for solar.

[Zakalwe]

2 hours ago, kirkster501 said:

I'm not using the TEC for the Quark, certainly not yet, and when/if I do I would buy an ERF.  However, to address your point the TEC is completely fine for white light solar and a Herschel Wedge.  Done so many times with Yuri's - the manufacturers - blessing.  He says, and I agree (FWIW) that the objective is just like a piece of glass on the table.  It is only when the rays come to focus when all the fireworks start.  Yuri says he has folks using his TEC200s perfectly fine for solar.

I'd trust the word of the guy who made the scope.

Daystar specifically do not recommend using an oil spaced refractor without a ERF, but this may be ass-covering?  http://www.daystarfilters.com/inout_article_base/index.php?page=view/article/4/UVIR-Cut-Filter-application-for-Refractors

I suppose there's also a chance that the heat energy rejected by the ERF could come to focus inside the objective. That'd be through a freak of spacing where the internal ERF is located in precisely the wrong spot. All that energy has to go somewhere...sometimes the focal point is inside the OTA where it can heat the air causing currents. Mostly I would guess that the rejected energy comes to focus outside the OTA somewhere in front of the objective.

[Merlin66]

I use my Genesis 4" f5 with a Baader Cool Herschel wedge for solar white light imaging.

It's an urban myth that Petzval scopes can't safely be used for solar work.

I have it in writing from Takahashi, Williams Optics and TeleVue that all their Petzval designed scopes are safe to use with no ERF for white light observing with the wedge.

 

[Solar B]

The mirrored finish of the Quarks BF will reflect most of the energy back up the OTA

I certainly wouldn't recommend using a triplet without a full aperture ERF

and they're a big no no with cemented elements as I've seen images of those melting !

But as stated air spaced etalons are the best way to dip ones toes , I'm moving 

away from solid etalons again and its somewhat of a relief !

Brian 

 

 

 

 

Edited June 14, 2020 by Solar B

[Rusted]

My 6" f/8, with internal 90mm D-ERF, produced a fiercely hot, reflected focal point just outside the objective.
An ideal spot to hold your face when peering into the OTA to check for morning dew!
I literally set fire to a temporary cardboard ring white experimenting with stopping down.
Do these "big name" manufacturers approve of having a bonfire in the dewshield?
Break the piggy bank, on a full aperture D-ERF and protect your investment [and your eyes!]

[Zakalwe]

15 hours ago, Solar B said:

The mirrored finish of the Quarks BF will reflect most of the energy back up the OTA

I certainly wouldn't recommend using a triplet without a full aperture ERF

 

Ive been using Quarks with triplets for years. Currently using an Esprit 120 for 3 years and an Altair Astro 115 before that. No external ERF.

 

Cemented objectives are absolutely a no-go zone.