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Venus (Feb 4) Mars (Feb 5) With Filters.

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#1 David Gray

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Posted 05 February 2017 - 02:20 PM

Nice view of Venus last night with the D-K but Mars too near rooftops before I could pick it up.

 

Tonight it did not clear soon enough for another shot at Venus with the big scope – so set up

the other end of the garden with the SW refractor.  Mars was so crisp I concentrated on that;

and just in time before cloud arrived.

 

Dave.

 

Edit Note:The Venus views are North-up / East Left - that Amici keeps messing me up.....!

Venus Mars 2017 Feb 4 5.jpg


Edited by David Gray, 05 February 2017 - 03:00 PM.

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#2 Special Ed

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Posted 05 February 2017 - 06:19 PM

David,

 

I like your views of Venus--especially the one with the W47 filter.  And your observational sketch of Mars coincides really well to the one that Chris posted.  Many thanks for posting.



#3 Sheliak_sp

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Posted 06 February 2017 - 01:00 AM

Very nice work david! It's so interesting to be able to compare different filters, and those clouds are very beautiful!

 

Migue



#4 Aquarellia

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Posted 06 February 2017 - 04:35 AM

Very nice sketches David, thank you to share that here!

Michel



#5 mariosi

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Posted 06 February 2017 - 09:33 AM

Excellent presentation Dave!

 

Marios



#6 David Gray

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Posted 06 February 2017 - 03:12 PM

Thanks everyone - very much appreciated..... :) 

 

Cheers,

Dave.



#7 PeterDob

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Posted 06 February 2017 - 03:14 PM

Simply stunning, David. The subtle hues and shadows make your sketches look like photographs. I'm so impressed...  :bow:  :bow:  :bow: 

 

Peter



#8 David Gray

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Posted 06 February 2017 - 04:47 PM

Many Thanks Peter.

 

Cheers,

Dave.



#9 chrisrnuttall

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Posted 06 February 2017 - 04:49 PM

Dave

I'm impressed with the banding on Venus, this has eluded me of late as the phase shrinks.

I haven't tried a green filter on Venus recently, do you find your stack gives better results than the violet W47 (which I love and always use)?

 

I have superimposed the curves from the three filters in the stack and created the band pass curve for the combination.

It's quite a narrow green, and with the addition of the 80A you cut the total transmission down which must be useful in your light bucket!

 

Interesting note for users of smaller scopes is that the same stack could be used without the 80A to give the same wavelengths but with more light transmission.

Attached Thumbnails

  • Daves Venus Stack.jpg

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#10 David Gray

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Posted 06 February 2017 - 05:25 PM

Yes I agree #15+#58 works very well - and others have tried it - used to be my default combo -

the #80A addition came along later years.

 

That deep blue filter: #47B is much darker than the regular #47, and needs good transparency

even with the D-K and often have to leave the apodizer off - unless it is monovu not bino..

 

The #47B practically eliminates red light altogether as can verified with the bright embers of a fire,

​where they are practically invisible but well apparent in the #47.  Richard McKim prefers the #47B

but apart from getting the Kodak gelatine type I do not see it advertised these days

 

In fact my Celestron #38A lets less red through than their #47......!

 

Dave. 

 

EDIT-here we go again........!

Venus 2015 April 5 1450 1555.jpg


Edited by David Gray, 06 February 2017 - 05:42 PM.

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#11 Special Ed

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Posted 06 February 2017 - 09:42 PM

I've had some luck with the W80A and W11 stacked.  This was with my 8" scope.

 

Venus_6.10.07.v1.JPG


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#12 David Gray

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Posted 07 February 2017 - 01:03 PM

Yes I can see that combo working – I have a number to try when I can.

 

Attached is my collection; and have since that photo added #11, #12, #21.  The ones marked BAS are from the custom-builders of the D-K – the #22 I actually prefer over the #23A.  Their #85 was sold as a planetary-contrast filter but not used it much.  A 2” Baader Neodymium is not shown.

 

Hopefully the photo shows the darkness of the #47B v the #47.  Never know how these attachments are going to show on other monitors etc.; but, after a number of attempts, I got the shot here by placing them on thin white paper laid across a mirror on a bright day with the sun out of sight.  Looks pretty close on my screens anyhow!

 

Dave.

 

FILTERS.jpg



#13 azure1961p

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Posted 07 February 2017 - 02:57 PM

I may just go get that 29 Dave. If it's too dense for Mars it'd be dynamite on the moon, particularly in bad seeing. More over, I'm thinking of getting another 47 to replace the one I damaged. Lousy and diffuse with light scatter on the moon but excellent on Venus.

 

 

Mars is looking good here, and Chris Nuttles favourably agrees with your view.  My only persistent observation , granted mostly with a small mak as of late, is one featureless band of Maria across its face. Period.  It's just a rough go, particularly because of the planet's location over rooftops at sunset.

 

Venus for me is like Uranus and Neptune, I don't observe it enough. Again the location from home for Venus is lousy and perhaps casualness for the outer gas giants. 

 

Lots of great illustrations here Dave, Chris' contribution is appreciated.

 

Pete



#14 chrisrnuttall

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Posted 07 February 2017 - 03:42 PM

Dave, I didn't notice the B, thanks for putting it in bold for me! Have to confess I have never heard of it before.

I just went and tested the red transmission of my W47. It lets no red light through at all, which might be why I get such great views with it. Whenever I use it I get the impression of being at a kids disco where everything is glowing violet under black-lights.

 

Here is a photo of my 2x1watt LED red bike light through the W47 (and without). This red LED light is blindingly bright, but as you can see all that gets through the W47 is a teeny weeny bit of yellow. (in the unfiltered view the middle of the light looks white, but I very much suspect that it just overwhelmed the CCD in my phone.)

Bear in mind also that the camera has auto adjusted the exposure between the two shots and the difference is far greater than shown here.

Sadly I don't know what brand the W47 is because it is unmarked. But I might be able to find out.

Attached Thumbnails

  • lights.JPG
  • Filters.JPG


#15 niteskystargazer

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Posted 07 February 2017 - 04:16 PM

Dave,

 

 Nice sketches of Venus & Mars :) .

 

CS,KLU,

 

:thanx: ,

 

Tom



#16 David Gray

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Posted 10 February 2017 - 12:33 PM

Sorry for the slow response - Internet down - lost the plot a bit.....but many Thanks to those I missed.....the Likes and all.......

 

Chris…….took me a while to find it: but I have tried the red-LED bike light (Cateye) and both the 47 & 47B perform much as you describe with your 47.  Then I coupled each in turn (and 38A) with a #25 red and could barely see the light (sky) through the window with the 47B – but somewhat more distinct with the 47 and rather more distinct still with the 38A;  moderately light even-grey sky at the time.

 

So a bit perplexed at this point…..what does perform best (think I needs dark-adapt!) is the piece of 47B Kodak Wratten gelatine with the #25.  Richard McKim had given me some years ago (maybe 25-30 ago…!); think I’ll check it out next time with Venus – whenever that might be……….

 

Pete……..I like the #29 and maybe you could get good lunar views – in the meantime maybe try stacked combos with #15, #21, #23A or #25 – or maybe three of them!

 

Dave.


Edited by David Gray, 10 February 2017 - 12:56 PM.


#17 frank5817

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Posted 10 February 2017 - 02:24 PM

David,

 

Very fine work here.

Good thread above.

 

I like the useful information you posted on filter for Venus.

 and of course the great looking sketches.

 

Frank :)


Edited by frank5817, 10 February 2017 - 02:25 PM.


#18 chrisrnuttall

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Posted 11 February 2017 - 08:34 AM

Dave

 

I am guessing it is to do with the shape of the band-pass curves for the filters. Perhaps your 47 passes a little more orange than your 47B?

Possibly best not to get too hung up about though!

 

I will definitely try your Venus-stack next time the rain stops and let everyone know how I get on with it.



#19 ericjam

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Posted 11 February 2017 - 01:14 PM

Hi David,

 

Wonderful sketches as always!

 

And thanks for all the info on the filters.

 

 

Best,

 

Eric 

 

 

 

http://ejamison.net/

 

 


Edited by ericjam, 11 February 2017 - 01:19 PM.


#20 David Gray

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Posted 12 February 2017 - 08:23 AM

Many Thanks Frank, Eric......

 

You might like to follow to the link I give to Chris below the Quote......

 

Dave

 

 

Dave

 

I am guessing it is to do with the shape of the band-pass curves for the filters. Perhaps your 47 passes a little more orange than your 47B?

Possibly best not to get too hung up about though!

 

I will definitely try your Venus-stack next time the rain stops and let everyone know how I get on with it.

OK Chris………. I have had a suspicion for some time that original Wratten specifications are not strictly adhered to among the various manufacturers of the glass types we commonly find for some years now.  What I do avoid are those who simply describe/sell their filters as a “Red one a “Blue” one etc………That apart:   as I have said elsewhere (often!): I’m a suck-it-and-see guy and if what I see does the job that’s fine.

 

Those worries with Richard McKim (BAA Mars) about him preferring 47B over the 47 red-leak was in those days when there was more concern for consistency among visual observers.  Imagery pretty much blew those concerns away as not too many care (or even know) about that in these times with regard to visual.  I still address such concerns with my own work;  for observing practice/principles not to mention self-respect.

 

I contributed to a thread on the Eyepiece Forum that might be of interest where the OP did some analysis of stacking-combos I mentioned. That follows through from my post #7 on there.

 

http://www.cloudynig...s/#entry7168297

 

I guess you are similarly afflicted with the same prolonged dreary weather that have we here……….

 

Dave.




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