Venus from April

[Pete Presland]

The amount of time i have spent processing these images has been probably too long. Trying to get somewhere near the magnificent images by @CraigT82 @lukebl and co has been a mission 🙂  Not sure that my SCT scope will allow enough signal through compared to large newts due to the coatings.  (maybe aperture fever is going strike again)

Been great fun capturing, processing and chatting to others who have imaging this wonderful target in the UV wavelength! not managed a presentable "false colour" image yet though. 

The data is saved so i will still have that to play with.   All images captured with C9.25, Asi 290mm, X1.8 Barlow. 

 

[Stargazer33]

It looks like you've managed to capture some cloud albedo in the top 3 images Pete

[Pete Presland]

4 minutes ago, Stargazer33 said:

It looks like you've managed to capture some cloud albedo in the top 3 images Pete

Yes definitely got some, i will probably have another play with the data over the summer.

[CraigT82]

Great images Pete, plenty of detail there. Yes I think that schmidt corrector plate is a bit of a disadvantage in UV. 

Edited May 6, 2020 by CraigT82

[Merlin66]

Pretty good!

What filters (if any) were you using?

3 hours ago, CraigT82 said:

Yes I think that schmidt corrector plate is a bit of a disadvantage in UV

Craig,

I question this..I've been using an SCT (C11) for many years for spectroscopy and can get down to 3700A (in the UV) with no issue. The camera response curve is more of a concern, it drops quickly to zero below 4000A.

 

[Pete Presland]

That is an interesting graph, assuming the figures at the bottom are the wavelength. What do the figures at the side represent?

[Merlin66]

Yes,

The X axis is calibrated wavelength in Angstroms, the Y axis is arbitrary intensity levels of the spectral plot.

You can see a reflection of the camera QE curve and the underlying spectral intensity of the star.... the intensity at 4200A is around 90K and drops to <10K(?) by 3700A.

The actual Plank curve of an A type star in this area peaks around 4000A then drops off towards the Balmer limit at 3650A.....

[CraigT82]

I've no doubt that UV light gets through the corrector. Just a bit less UV light than non corrector scopes. Hence a slight disadvantage... though probably hardly measurable I guess 

[Merlin66]

Craig,

I think you're comparing a reflector (all mirror elements) with any other telescope......

I've used both and honestly can't tell the difference down in the UV.

(My ol' Genesis 4" f5 Petzval 4 element design gave good spectra down to the Balmer limit.)

 

 

[lukebl]

Thanks for the complement Pete, but I think your captures are superb and I think you can also tease a bit more detail out of them with a bit of a play in Photoshop.

Last night I had an exceptional period of clarity and great seeing, so thought I'd capture some great detail. However, I'm processing the captures now and they seem to have almost no detail at all even though the images are sharp. I wonder if the solar lighting angle at the current phase makes the clouds less visible? The clouds were certainly clearer at half and gibbous phase, even though the disc was smaller.

[Star101]

Great capture on Venus there. 👍

I had a go at imaging Venus last night, still to process. Its much smaller crescent now so I doubt I will get enough detail to see the clouds as good as you have here.

 

[Pete Presland]

7 hours ago, lukebl said:

Thanks for the complement Pete, but I think your captures are superb and I think you can also tease a bit more detail out of them with a bit of a play in Photoshop.

Last night I had an exceptional period of clarity and great seeing, so thought I'd capture some great detail. However, I'm processing the captures now and they seem to have almost no detail at all even though the images are sharp. I wonder if the solar lighting angle at the current phase makes the clouds less visible? The clouds were certainly clearer at half and gibbous phase, even though the disc was smaller.

I certainly think the phase is probably a bit small now. I prefer to see at least 50%, oddly Venus does seem to be smaller than the actual "advertised" size. 

[Pete Presland]

7 hours ago, Star101 said:

Great capture on Venus there. 👍

I had a go at imaging Venus last night, still to process. Its much smaller crescent now so I doubt I will get enough detail to see the clouds as good as you have here.

 

looking forward to seeing that crescent get thinner and larger over the coming weeks.

[Pete Presland]

9 hours ago, Merlin66 said:

Yes,

The X axis is calibrated wavelength in Angstroms, the Y axis is arbitrary intensity levels of the spectral plot.

You can see a reflection of the camera QE curve and the underlying spectral intensity of the star.... the intensity at 4200A is around 90K and drops to <10K(?) by 3700A.

The actual Plank curve of an A type star in this area peaks around 4000A then drops off towards the Balmer limit at 3650A.....

It seems very difficult to get much info on the QE curve of the cameras below 400nm.

[John]

I guess we wont be able to see it as thin as we could last time around because Venus will get too close to the Sun for safe observation in due course ?

I got this far last time (simulated view) - mikeDnight got it a bit thinner I seem to recall ?

 

[Pete Presland]

6 minutes ago, John said:

I guess we wont be able to see it as thin as we could last time around because Venus will get too close to the Sun for safe observation in due course ?

I got this far last time (simulated view) - mikeDnight got it a bit thinner I seem to recall ?

 

WOW, look at that! That is proper thin!  I think i managed a 3 degree phase last time.

You are correct John, isn't it going to be a couple of degrees away from the Sun at opposition this time, as opposed to 8 degrees last time?

[Tommohawk]

On 07/05/2020 at 09:21, lukebl said:

I wonder if the solar lighting angle at the current phase makes the clouds less visible

That's an interesting idea - maybe so. Well that's my excuse anyhow!

[orion25]

Great work as always, Pete! Nice cloud detail  

Regards,

Reggie