UHC Filter: ES or Astronomik

[rwilkey]

On 04/05/2020 at 17:54, miguel87 said:

'm saving my cash for the astronomik UHC. Cant decide whether to get 1.25" or 2".

I only have one 2" eyepiece,

Hi Miguel, always go for 2" as you can use these with either 2" or 1.25" ep's by attaching the filter to the 2" end of your adapter, you don't need to attach filters to ep's at all and it saves faffing about when you switch ep's.  A filter can be placed in any part of the focal chain.

Edited May 10, 2020 by rwilkey

[miguel87]

26 minutes ago, rwilkey said:

Hi Miguel, always go for 2" as you can use these with either 2" or 1.25" ep's by attaching the filter to the 2" end of your adapter, you don't need to attach filters to ep's at all and it saves faffing about when you switch ep's.  A filter can be placed in any part of the focal chain.

Thanks for the tip. I'm not sure about attaching to the end of the adaptor tho?

My 1.25 to 2 inch adaptor is just flanged at the end and tightened with two finger screws as if it was an eyepiece.

Maybe I am missing something?

Also would there not then be a problem with reaching focus with a 1.25inch eyepiece?

Edited May 10, 2020 by miguel87

[John]

Skywatcher 1.25 inch eyepiece adapters are not usually threaded for filters, unfortunately.

 

 

[miguel87]

1 minute ago, John said:

Skywatcher 1.25 inch eyepiece adapters are not usually threaded for filters, unfortunately.

 

 

Thanks John, will check mine later when I am setting up. Fairly sure it is not threaded tho, shame as it would save me money!

Although I have been thinking about maybe going for the 1.25 inch filter anyway. I only have 1 plossl in my collection (20mm NPL) and it is my lightest (least glass) eyepiece by a good margin. I sometimes moan about it for not having a view that is as contrasty as other eyepieces.

Now I am thinking maybe this is because it allows the most light through and shows more sky glow. If this is the case, maybe it is the ideal EP for a filter to have a noticable effect. It is also my second longest focal length (after my 2inch eyepiece).

[bomberbaz]

I used to have a chart for exit pupils for various filters but generally the tighter the bandpass of a filter, the larger the exit pupil needs to be. This is because you are dramatically cutting the levels of light passing into your eye and therefore a larger exit pupil is needed to make the image being looked at bright enough.

As a UHC has a larger bandwidth passthrough than say a HB, you can get away with a smaller exit pupil.  However this also depends on the target option. EG planetary nebula such as the ring nebula are quite bright and so will stand a lower exit pupil, even down to 1mm and be viewed from a light polluted back garden.

The horshead nebula on the other hand is very dull object, really needs a HB filter and a 5mm exit pupil is optimum. (in ink black skies)

Your 20mm plossl will give an exit pupil 3.3mm which is great for very many nebula.

Steve

Edited May 10, 2020 by bomberbaz

[miguel87]

8 minutes ago, bomberbaz said:

I used to have a chart for exit pupils for various filters but generally the tighter the bandpass of a filter, the larger the exit pupil needs to be. This is because you are dramatically cutting the levels of light passing into your eye and therefore a larger exit pupil is needed to make the image being looked at bright enough.

As a UHC has a larger bandwidth passthrough than say a HB, you can get away with a smaller exit pupil.  However this also depends on the target option. EG planetary nebula such as the ring nebula are quite bright and so will stand a lower exit pupil, even down to 1mm and be viewed from a light polluted back garden.

The horshead nebula on the other hand is very dull object, really needs a HB filter and a 5mm exit pupil is optimum. (in ink black skies)

Your 20mm plossl will give an exit pupil 3.3mm which is great for very many nebula.

Steve

Interesting thought Steve, didnt consider that. My 200p is the EQ so an even bigger pupil at 4mm should be ok with a UHC. Would be my first filter.

Edited May 10, 2020 by miguel87

[bomberbaz]

On 04/05/2020 at 14:27, Cuto100200 said:

Just looking into general purpose filters, discovered that generally UHC and ND filters are good all-rounders, with IIIO being a little more specific to certain objects.

The ES UHC is half the price of the Astronomik, how much higher quality will the Astronomik be at double the price, and would this be worth the price increase? 

ES: https://www.firstlightoptics.com/uhc-oiii-visual-filters/explore-scientific-uhc-nebula-filter-1-25-2-inch.html

Astronomik: https://www.firstlightoptics.com/uhc-oiii-visual-filters/astronomik-uhc-filter.html

 

Thanks

This link here is very useful to allow you to pick the right type of object to look at and also assist with your expectations of results.

https://www.cloudynights.com/articles/cat/user-reviews/accessories/astronomical-filters/filter-performance-comparisons-r1471#top

[rwilkey]

1 hour ago, miguel87 said:

Thanks for the tip. I'm not sure about attaching to the end of the adaptor tho?

My 1.25 to 2 inch adaptor is just flanged at the end and tightened with two finger screws as if it was an eyepiece.

Maybe I am missing something?

Also would there not then be a problem with reaching focus with a 1.25inch eyepiece?

Sorry Miguel, John above is quite right, it will not work with the SW 200P.  I haven't used mine since I became partially disabled a few years ago.  It works, of course, with refractors that have a 2" - 1.25" adaptor or a diagonal. 

The use of filters has no impact at all on focus.

[bomberbaz]

The 2 to 1.25 adaptors can be found cheap enough on ebay or similar. I found this one on sale which appears to be threaded and is compression ringed for eyepiece holding. It would be a good idea to check re: threaded or not first though as it is coming from china.

adaptor

Steve

[bingevader]

Yes indeed.

I have a 1.25" to 2" adaptor from Revelation Astro.

Not as cheap as ebay, but threaded.

I bought mine to use my (1.25") 14mm ep whilst using my 2" eps.

Means I don't have to swap everything out when swapping between.