Hydrogen Alpha filter

[wookie1965]

Can you get one of these to fit on a 4" refractor I was watching Sky At Night this morning and Pete Lawrence had one on his just wanted to see if I could get one thanks. 

[Stu]

2 minutes ago, wookie1965 said:

Can you get one of these to fit on a 4" refractor I was watching Sky At Night this morning and Pete Lawrence had one on his just wanted to see if I could get one thanks. 

Do you mean for observing solar hydrogen alpha features like prominences and filaments Paul?

[wookie1965]

25 minutes ago, Stu said:

Do you mean for observing solar hydrogen alpha features like prominences and filaments Paul?

Yes Stu exactly that thanks. 

[Highburymark]

You can - but the full aperture Ha solar filters (available from Lunt or Solarscope. Coronado also make them but don’t seem to sell most of them separately) are pricier than smaller internal etalons/filters as part of dedicated solar telescopes. Pic is example of solar filters on TV85. You just need to buy an adapter to fit them to the refractor of your choice.

[Highburymark]

Plus you need an additional ‘blocking filter’ at the eyepiece end - it’s the section marked with blue tape in the pic above…..

[Elp]

To put it simply (in case a newbie sees this):

DO NOT USE OR BUY A HA FILTER ONLY AND USE IT TO LOOK AT OR PHOTOGRAPH THE SUN.

To see ha features of the sun you need:

1. A dedicated solar telescope like a Lunt Solar, Coronado Solarmax, Coronado PST or Daystar Solar Scout. These have the necessary blocking filters and ha narrowband filters to allow safe ha viewing.

Or 2. A Daystar Quark which is like 1 but compressed into an eyepiece unit which can be usb powered in order for the internal etalon to reach bandpass for ha viewing. Note, if using in a telescope larger than 90-100mm aperture you'll need a DERF (energy rejection filter) in front of the objective to minimise the massive heat and UV/IR radiation entering the scope. A 35nm ha filter in front of the diagonal and quark can help with the smaller apertures, larger apertures need a DERF. Small scopes (below 80mm) can get away with a UV/IR cut filter in front of the diagonal and quark, it's more to protect the amount of energy getting to the quark in this case.

Or 3. I only read of people using refractors as they're easier and slightly cheaper to buy erfs for (but you can use mirror scopes too), you can use a current refractor which is all metal construction and not oil spaced with its objectives, you'll need to purchase a DERF larger than the front objective to cover it, then use a Coronado PST back end (newer PST which has the blue/green ITF in the eyepiece holder section after the pentaprism) which has the (working) blocking filter and ITF (bandpass) filter to view ha features.

You CAN use a ha filter at night to help filter out LP and allow ha rich emission nebula to filter through as an aid, I believe human eyes are not particularly colour sensitive to the ha bandpass though for night time viewing, more like monochromatic sensitive.

Edited June 13, 2023 by Elp

[michael.h.f.wilkinson]

If you have an 80 mm refractor with focal ratio between 4 and 8, the Quark is probably the best choice. Note that while an ERF or DERF is not strictly needed for both the Quark, adding one keeps the temperature in the OTA down, and thus reduces tube currents. I have a Tri-Band ERF which transmits light around Ca-K, the solar continuum band, and H-alpha, and using it both for white light and Ca-K really improves image quality (neither the Herschel wedge nor the Ca-K module I have require an ERF).

Note that there are Tri-Band SCTs in which the corrector plate is coated in such a way it transmits bands around Ca-K, O-III, and H-alpha. Expensive, but can give really high resolution images of the solar surface.

[Highburymark]

Yep. Good safety points from elp - any solar observing is potentially disastrous without the right equipment.

Anyone looking to get into Ha solar for the first time - and it’s a fascinating part of the hobby - the cheapest option is a secondhand PST or Lunt 35. Around £500 up. Quarks come up regularly on the classifieds for around £750 upwards secondhand, and as Michael points out are a good option if you want to convert an existing scope. 

[michael.h.f.wilkinson]

A second-hand Lunt 35 was my first foray into H-alpha. Apparently, it is not suitable for imaging, but I simply ignored that

[knobby]

naughty but nice 🙂

 

[wookie1965]

This is from the Sky at Night now what's on the back of his refractor please so I can price them up. 

 

 

Edited June 17, 2023 by wookie1965

[Franklin]

Think you've posted the wrong clip @wookie1965.

[wookie1965]

1 minute ago, Franklin said:

Think you've posted the wrong clip @wookie1965.

I posted it from my phone on there I realised my mistake and deleted it how or why it stayed on I have no idea.

[wookie1965]

Does the clip play?

[Knighty2112]

Clips plays OK from here. 👍🏻

[Elp]

1 hour ago, wookie1965 said:

what's on the back

Not quite clear but I'd say it's a Daystar Quark with a zwo camera in the back end. The standard ha quark comes in two varieties a chromosphere and prominence model which have etalons tuned at slightly different bandpasses so the prominence allows viewing of prominences better. The chromosphere one however can also see prominences so is the one people typically buy.

If you're using a 90mm plus refractor it might be advisable to also get a 35nm ha filter to put onto the front of your diagonal if you use one, or in front of the quark if viewing or imaging straight through. Bare minimum use a UV/ir cut filter. For smaller refractors one isn't necessary, but for precaution it "could" possibly extend the life of the quark.

Quarks do tend to have a quality lottery so best to buy from a reliable source in case you get a bad one.

[Neil H]

FLO check all the daystar units so you know it's ok I got my solarscout from them and it's spot on 

[Franklin]

Its a Daystar Quark, I picked one up today and it's brill.

[Nigella Bryant]

On 17/06/2023 at 07:44, wookie1965 said:

This is from the Sky at Night now what's on the back of his refractor please so I can price them up. 

 

 

That's a calcium iik filter, CaK, image. Using probably something like a lunt cak module. 

[BGazing]

@wookie1965 you can certainly fit Daystar Chromosphere to the back of your Tal, but I think you would be better served by buying a small dedicated solar scope. 

I had a Daystar and used it with my 70 and 100mm refractors. The trick is, my 100mm refractor is f/7.4 and the Quark has an internal 4.2x telecentric barlow. Meaning that your Tal will be operating at f/42 and you would be limited to 40mm Plossl - which means uncomfortable views and high magnifications (which you do not always want in h-alpha). I had another refractor to play with. Eventually I decided I like h-alpha so much that I bought a Lunt 80, now double stacked.

I do not regret buying Quark, but I think getting a small dedicated h-alpha telescope is a better purchase and a better bang for the buck.

[wookie1965]

1 minute ago, BGazing said:

@wookie1965 you can certainly fit Daystar Chromosphere to the back of your Tal, but I think you would be better served by buying a small dedicated solar scope. 

I had a Daystar and used it with my 70 and 100mm refractors. The trick is, my 100mm refractor is f/7.4 and the Quark has an internal 4.2x telecentric barlow. Meaning that your Tal will be operating at f/42 and you would be limited to 40mm Plossl - which means uncomfortable views and high magnifications (which you do not always want in h-alpha). I had another refractor to play with. Eventually I decided I like h-alpha so much that I bought a Lunt 80, now double stacked.

I do not regret buying Quark, but I think getting a small dedicated h-alpha telescope is a better purchase and a better bang for the buck.

Thank you so much really appreciate it very informed information there I can take on board.