Sub Aperture ERF Options For Quarks

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skyhawk
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Sub Aperture ERF Options For Quarks

Post by skyhawk » Sat May 04, 2019 2:21 pm

I know there are cheap and expensive filters available, just as a Rolls Royce is better than a Ford Focus, but............ they are still cars, legal and get you from a-b

Filters. There are these

https://www.ebay.co.uk/i/183268614612?chn=ps


and these

https://www.widescreen-centre.co.uk/ida ... ilter.html

and these

https://www.widescreen-centre.co.uk/baa ... 317mm.html

etc

I have the first one, (a) is it OK ?, (b) would the Baader be better and if so how, (c) if the one I have is not any good how will I know. What would you suggest for in front of the diagonal with a Quark Cromo as an IR blocking (heat) filter

Many thanks indeed


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Re: I know there are cheap and expensive

Post by krakatoa1883 » Sat May 04, 2019 4:39 pm

Hi

Let's look at the transmission curves of all these filters

Svbony
UVIR Svbony.jpg
UVIR Svbony.jpg (17.64 KiB) Viewed 767 times
IDAS
idas.jpg
idas.jpg (45.89 KiB) Viewed 767 times
Baader Neodymium
baader-neodymium-1-1-4-moon-skyglow-filter-001.jpg
baader-neodymium-1-1-4-moon-skyglow-filter-001.jpg (41.73 KiB) Viewed 767 times
Outside the range 400 (450) - 700 nm they all look about the same, with some differences which are not relevant for H alpha observing, so if the declared curves are reliable there would be no reason to prefer one over the others.

I personally (just my opinion) would not use the cheapest one, filters shall not only block the undesired wavelengths but shall also be finely polished and very well coated, so I would take only the best available ones.

In front of my Quark I normally use a L-2 Astronomik UV/IR cut which has the following transmission
Astronomik_filtro_L_descrizione.jpg
Astronomik_filtro_L_descrizione.jpg (48.76 KiB) Viewed 767 times
quite similar to the filters above. I sometimes use also the Baader equivalent (this one) or even a deep sky H-alpha filter.
skyhawk wrote:
Sat May 04, 2019 2:21 pm
(c) if the one I have is not any good how will I know.
good question with no easy answer, it would require to determine the transmission curve.

Hope it helps


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Re: I know there are cheap and expensive

Post by christian viladrich » Sat May 04, 2019 7:51 pm

There is no free lunch the saying goes :-)


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Re: I know there are cheap and expensive

Post by RodAstro » Sat May 04, 2019 11:54 pm

Hi
I have two of the sVboney a beloptic and the baader have also tried the baader 35nm all give the same results for solar.
The beloptic is on KG3 glass so may have more protection.
Personally I would use the one you already have and save your money to put towards a D-ERF.
The quark has a good blocker all the UV/IR is doing is protecting it from degrading a D-ERF protects everything and removes tube currents that will result in better seeing.



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Re: Sub Aperture ERF Options For Quarks

Post by marktownley » Sun May 05, 2019 9:36 pm

For me it's like what Christian says. My experience is that the cheaper option stops working at some point before you anticipate.


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Re: Sub Aperture ERF Options For Quarks

Post by RodAstro » Sun May 05, 2019 10:12 pm

Hi
You could try this at the front it would stop quite a bit of heat buildup in the scope

https://www.ebay.co.uk/itm/B-W-UV-IR-Sp ... 1438.l2649

The graph seems to fit the bill and as far as I can remember B+W filters are polished 1/4 wave much better than most camera filters.

Just a idea of another option.
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