Backyard astronomers, how do you decide what to look at?

[sophiecentaur]

or polarizing filter

I’m not so sure that the reduction in luminosity is great enough with polarisers . Iirc, my ND is 12% and even that’s pretty bright.

 

[Nick-stg]

I don't know much about these filters. I just checked out real quickly what is available and prices range from $40 for the polarizing filters to in excess of $300 for UHC filters. What's what, I assume that you get what you pay for, what's the benefit and what is the sweet spot? Or maybe this is a topic for a new thread?

 

[sophiecentaur]

An ND filter need only cost a few quid. No need to go mad.

 

[Nick-stg]

I have an ND96 moon filter. Is that going to help see faint nebulae?

 

[George Jones]

I have an ND96 moon filter. Is that going to help see faint nebulae?

No, just the opposite.

A moon filter reduces the intensity of all wavelengths, including wavelengths typically emitted by nebulae. A moon filter is to be used when looking at the moon with you scope.

On the other hand, a UHC filter reduces the intensity of all wavelengths, except wavelengths typically emitted by nebulae, which get transmitted normally, i.e., backgound light is reduced much more than light from nebulae.

 

[Nick-stg]

On the other hand, a UHC filter reduces the intensity of all wavelengths, except wavelengths typically emitted by nebulae,

That was my understanding. Thank you for confirming. But what about the h-alpha, h-beta, O-III etc.. based on their descriptions these appear to do the same thing as the UHC filters. What's the difference?

 

[George Jones]

That was my understanding. Thank you for confirming. But what about the h-alpha, h-beta, O-III etc.. based on their descriptions these appear to do the same thing as the UHC filters. What's the difference?

While I have an 8-inch scope, I don't own any filters, and I am not much of a guide for them. Try

https://starizona.com/tutorial/narrowband-imaging/

 

[lomidrevo]

I’m not so sure that the reduction in luminosity is great enough with polarisers . Iirc, my ND is 12% and even that’s pretty bright.

on the filter I got (Orion Variable Polarizing Filter), you can adjust the amount of light transmission from 1% to 40%. Very practical, as you can appreciate different transmission in case of full moon, and different one in case of observing Jupiter (I noticed that some very fine details can be enhaced by using the filter even with Jupiter).

 

[russ_watters]

But what about the h-alpha, h-beta, O-III etc.. based on their descriptions these appear to do the same thing as the UHC filters. What's the difference?

Narrow-band vs broad band. Those that specifically identify an emission line block everything except that emission line. UHC filters have a broad band of what they let in and/or a narrow band of what they block (sodium-sulphur lines from street lights, for example). It's all described in the product details:

https://www.highpointscientific.com...AlF9u7D3DkxBz0fxXVsgV4eoO03C9h_caArNcEALw_wcB

 

[sophiecentaur]

on the filter I got (Orion Variable Polarizing Filter), you can adjust the amount of light transmission from 1% to 40%. Very practical, as you can appreciate different transmission in case of full moon, and different one in case of observing Jupiter (I noticed that some very fine details can be enhaced by using the filter even with Jupiter).

I totally agree. I never bought those. Probably more expensive than an nd filter? I must admit that I was commenting on a straight photographic polar

 

[sophiecentaur]

That was my understanding. Thank you for confirming. But what about the h-alpha, h-beta, O-III etc.. based on their descriptions these appear to do the same thing as the UHC filters. What's the difference?

The UHC filter idea is a compromise between cutting out what you don't want to see (visually) and letting as much in that you do want. The resulting image is not quite as bright, of course but if you exclude nearby light sources and get light adapted, you can see a lot and the contrast is improved, of course. Astrophotography uses narrow band filters, for instance H-alpha (which will show you virtually nothing visually) and you use long exposure times (tracking and possibly guiding needed). Separate exposures with each filter produce a set of images which can be mixed to taste.

 

[chemisttree]

Narrowband one shot filters are really nice for color cameras too. I can’t believe the prices though. Waaaay outta my league.

https://astrobackyard.com/wp-content/uploads/2019/06/lagoon-and-trifid-nebula.jpg

$1075 for a 2” filter!

 

[sophiecentaur]

I can’t believe the prices though

Annoying innit? But think of the man-hours in quality checking and the cost of low volume sales. Then realize that 'enthusiasts' in any field are suckers. At least you can measure the results here - unlike with the snake oil that goes into most HiFi equipment.

 

[Nick-stg]

unlike with the snake oil that goes into most HiFi equipment.

Don't get me started on that one...