Venus (and Moon) through a Herschel Wedge

[Stu]

I currently have the somewhat ludicrous luxury of owning two Baader CoolWedges, so decided to try out the Mark I version with no filters fitted on Venus as I had heard this can help to cut the glare and improve the views.

Removing the filters was an easy job, and despite the hazy cloud I popped the scope out and picked Venus and the Moon up at around 20.44.

I can safely say that it was a successful experiment. Venus was sharper and dimmer, and as a result it actually showed some variation in surface brightness. This was largely a dimming towards the terminator but there was also some subtle difference in brightness running across this too. It’s the most convincing view of some sort of cloud visibility I’ve had, so I’ll keep on trying this approach.

Whilst I had the Wedge fitted, I tried an experiment which was doing a Facebook  Live broadcast. It is often very hard to control exposure on these, and the Wedge really helped this. I was able to run a live broadcast which maintained correct exposure even without zooming in, and I had none of the usual nonsense of the image flashing off and on when I got to higher zoom settings. It worked very well and I did a couple of broadcasts to different groups which worked well, including Venus as well.

So, I can recommend this as something to try, but PLEASE be careful to refit the filters before viewing the Sun again as it would be catastrophic to view without them. I would do it immediately after finishing so there is no chance of forgetting.

[saac]

I caught a glimpse of them last night just before I went to bed, they look absolutely stunning at the moment. That is a lovely image Stu, quite a neat solution as well. 

Jim 

[Mr Spock]

Interesting solution. I observe Venus with a variable polarising filter and a 80A blue filter. Variations in surface brightness are there once you get Venus down to the right 'dimness'.

[Littleguy80]

Really interesting, Stu. I've never heard of this approach. The TS Optics wedge I have makes this quite easy to do so will have to give this a go. Good shout on replacing filters immeadiately afterwards. Too easy to forget otherwise.

[Stu]

1 hour ago, Mr Spock said:

Interesting solution. I observe Venus with a variable polarising filter and a 80A blue filter. Variations in surface brightness are there once you get Venus down to the right 'dimness'.

I think it would be worth me trying a few coloured filters as well, to see if that helps bring out the detail better. Think I’ve got some squirrelled away somewhere.

[Paz]

That is interesting thanks for posting. I've had some success on Venus recently with an nd1.8 filter and also by stacking colour filters with a nd0.9 filter. A herschel wedge would do a lot of the dimming work but with fewer surfaces and fewer bits of glass in the light path. I'll give it a try.

[Stu]

I knew I had seen it mentioned on here before. My old friend @Moonshane used to use his wedge in a similar way. Hope alls well with you Shane if you see this 👍

 

[Louis D]

Short of using a perfectly cleaved crystal surface or a vacuum sputtered crystal surface, a Herschel wedge's uncoated first surface mirror should yield just about the smoothest, lowest scatter diagonal surface possible.  And, unlike a prism diagonal which has a similarly smooth surface, there is no possibility of introducing chromatic aberrations into the image.  Thus, it probably would yield the highest contrast possible for ultra-bright objects short of straight through viewing.  Of course, with straighter through viewing, you'd probably have to introduce some sort of dimming filtration, and that could add scatter itself.

For those not familiar with the internals of a Herschel wedge, I've attached a Wikipedia diagram below:

[Paz]

I've got my C8 set up with a wedge for tonight on Venus. The moon looks pretty good, it will be interesting to see how it goes when the scope is cooled and the sky dims a bit.

[Alan White]

Interesting idea and good on you for trying this out @Stu.

I observe Venus as per Michaels method, but with a fixed nd rather than a variable one.

[Mr Spock]

Yesterday I ordered a darker blue and a violet filter. I'll see if they make a difference.

[Louis D]

On 27/05/2023 at 04:45, Mr Spock said:

Yesterday I ordered a darker blue and a violet filter. I'll see if they make a difference.

I would think a pure blue filter like that used for RGB color separation coupled with a variable ND filter would be ideal for experimentation.

[Littleguy80]

I gave this a try tonight. Worked really well with Venus. I also felt that cloud detail along the terminator was perhaps easier to see. Venus perhaps wasn’t as sharp though this may well be due to seeing.

I was less keen when using it with the moon. It just felt too dark though maybe it would work better with larger scopes. I like the bright views and don’t use a polarising filter with a normal diagonal and my 100mm scope. 
 

[Stu]

48 minutes ago, Littleguy80 said:

I gave this a try tonight. Worked really well with Venus. I also felt that cloud detail along the terminator was perhaps easier to see. Venus perhaps wasn’t as sharp though this may well be due to seeing.

I was less keen when using it with the moon. It just felt too dark though maybe it would work better with larger scopes. I like the bright views and don’t use a polarising filter with a normal diagonal and my 100mm scope. 
 

Glad you found it useful on Jupiter Neil. I tend to agree on the Moon, though certain brighter features may benefit as it helps reduce the glare.

[Littleguy80]

10 minutes ago, Stu said:

Glad you found it useful on Jupiter Neil. I tend to agree on the Moon, though certain brighter features may benefit as it helps reduce the glare.

Really worthwhile experiment and something I would never have thought to try without this post so thank you! Will definitely use this approach with Venus again. Not so sure on the Moon but, as you say, there may be some features where it helps. 

[knobby]

I've used my imaging set up to capture the Moon during the day using the Ha filter, quite surreal to see it looking like midnight during the day. Might be worth a bash if anyone has an Ha filter ?