Sirius B and E/F stars - what does it take!?

[Geoff Barnes]

3 minutes ago, reezeh said:

You'd think someone would make an eyepiece with an occulting bar, or a thick wire (enough to block a star). I know, that's tantamount to cheating!

You've got me thinking now Robert, I wonder if sticking a strip of black tape over part of the bottom end of an eyepiece would work to block off the glare from a bright object like Sirius and enable the Pup to be seen???  ?

[John]

2 minutes ago, Geoff Barnes said:

You've got me thinking now Robert, I wonder if sticking a strip of black tape over part of the bottom end of an eyepiece would work to block off the glare from a bright object like Sirius and enable the Pup to be seen???  ?

Shane (Moonshane) and I tried adding occulting bars to ortho eyepieces to see the Pup star a few years back. It's worth a try but I can't recall that it worked for us back then. One issue is that the occulting edge itself seems to cause some additional diffraction which does not help with spotting the tiny gleam of the Pup star shining through the diffraction that surrounds Sirius A.

 

 

[Demonperformer]

Set up the scope with a wall to the west and wait for Sirius to go behind it? Should give you thirty see ones or so.

[reezeh]

3 hours ago, John said:

Shane (Moonshane) and I tried adding occulting bars to ortho eyepieces to see the Pup star a few years back. It's worth a try but I can't recall that it worked for us back then. One issue is that the occulting edge itself seems to cause some additional diffraction which does not help with spotting the tiny gleam of the Pup star shining through the diffraction that surrounds Sirius A.

 

 

Don't forget as well that the Pup has a fairly quick orbit around Sirius, about 48 years isn't it? Going from a wide double to much closer.

When you look is part of the matter; isn't the secondary about as far as it gets these days?

[reezeh]

3 hours ago, Geoff Barnes said:

You've got me thinking now Robert, I wonder if sticking a strip of black tape over part of the bottom end of an eyepiece would work to block off the glare from a bright object like Sirius and enable the Pup to be seen???  ?

Somehow I'm not sure that'll work, but I could be waaay wrong. I just keep thinking all you'll do is block some of the light as the occulting element should be at a point of focus, like in a viewfinder reticle - then it can be a wire just like in a viewfinder ... I think.

[reezeh]

Being honest isn't an occulting element how professional observatories image things like exoplanets and dust disks?

[Stu]

5 minutes ago, reezeh said:

When you look is part of the matter; isn't the secondary about as far as it gets these days?

Yep, current separation is 11.1", max around 2023 is 11.3" with minimum being 2.5" in 2042 ish. Makes you realise that to split it at its minimum must be all but impossible with amateur kit?

[Stu]

6 minutes ago, reezeh said:

Somehow I'm not sure that'll work, but I could be waaay wrong. I just keep thinking all you'll do is block some of the light as the occulting element should be at a point of focus, like in a viewfinder reticle - then it can be a wire just like in a viewfinder ... I think.

I agree, I think the occulting bar needs to be at or near the field stop so it is in focus.

[Doc]

I have seen E and F on a few occasions with my old 16" dob but have only ever seen the E star with my 120ED refractor. Sirius and the Pup on the other had was never visible in the dobsonian but I'm almost certain that I saw the pup once sitting just outside the diffraction ring in about the 10 o'clock position, it took a lot of effort and I had to sit under a blanket for 20 minutes before it appeared but I'm 95% certain I saw it.

[reezeh]

5 minutes ago, Stu said:

Yep, current separation is 11.1", max around 2023 is 11.3" with minimum being 2.5" in 2042 ish. Makes you realise that to split it at its minimum must be all but impossible with amateur kit?

I'm sure there's some lucky so-and-so somewhere calling him or herself an "amateur" who can stop their toy down by 90% and still do it at minimum separation.

[reezeh]

9 minutes ago, Stu said:

I agree, I think the occulting bar needs to be at or near the field stop so it is in focus.

It's either that or an enhanced version of @Demonperformer's idea of a wall. What's the "enhancement" I hear you ask... Well, build the wall on rollers far enough away to be at infinity focus and drive it in sync with your telescope. You'll be able to ogle the Pup as long as you want! ??

[Peter Drew]

37 minutes ago, reezeh said:

Don't forget as well that the Pup has a fairly quick orbit around Sirius, about 48 years isn't it? Going from a wide double to much closer.

When you look is part of the matter; isn't the secondary about as far as it gets these days?

 

This is why it took a 30" for me to see it around 40 years ago. Right now, a much smaller telescope can be successful, good seeing and tight star images are the key.   ?

[reezeh]

3 minutes ago, Peter Drew said:

 

This is why it took a 30" for me to see it around 40 years ago. Right now, a much smaller telescope can be successful, good seeing and tight star images are the key.   ?

Probably those living in low latitudes have a distinct advantage too methinks, Peter!

[John]

2 hours ago, reezeh said:

Don't forget as well that the Pup has a fairly quick orbit around Sirius, about 48 years isn't it? Going from a wide double to much closer.

When you look is part of the matter; isn't the secondary about as far as it gets these days?

I agree - the split is around the same as Rigel is from it's secondary star in terms of separation. If Sirius A was a couple of mags dimmer then it would be fairly routine.

[mikeDnight]

7 hours ago, reezeh said:

You'd think someone would make an eyepiece with an occulting bar, or a thick wire (enough to block a star). I know, that's tantamount to cheating!

Many years ago I blackened a match stick using a felt tip pen, then pushed it up against the field stop to act as an occulting bar. I wanted to block the light from Alnitak in the hope of detecting the Flame Nebula. The occulting bar idea worked but I didn't see the Flame on that occasion.

[John]

I wonder if an Apodizing mask / filter might be a suitable tool to help spot Sirus B ?:

https://www.telescope-optics.net/apodizing_mask.htm

This paragraph in the above information caught my eye (my boldening):

".....The two main opposing effects of this type of pupil apodizing are:
(1) improved contrast transfer for larger details, but decreased for those close to the limit of resolution, and
(2) impaired limiting stellar resolution, but improved resolution of unequal doubles with much fainter companion in the area of the first bright rings of the brighter principal star...."

Here is more on these things and how to make one. Might be useful for planetary observing as well - it was a popular tool in the past, apparently:

http://www.astronomyhints.com/apodize.html

 

[reezeh]

22 minutes ago, John said:

Here is more on these things and how to make one. Might be useful for planetary observing as well - it was a popular tool in the past, apparently:

http://www.astronomyhints.com/apodize.html

 

Quite what is meant by window screen? Is it that stuff Americans put on their doors to keep bugs out of the house? What mesh size, if that matters?

[reezeh]

52 minutes ago, mikeDnight said:

Many years ago I blackened a match stick using a felt tip pen, then pushed it up against the field stop to act as an occulting bar. I wanted to block the light from Alnitak in the hope of detecting the Flame Nebula. The occulting bar idea worked but I didn't see the Flame on that occasion.

Did you see anything worthwhile then, like help with any doubles? Even anecdotal recollections if you're happy to hit me with them.

[reezeh]

Is it realistic to 3d print an adjustable occulting bar that threads into eyepieces' filter threads, with a centre that can be screwed in and out to get the bar up to the field stop? ?

[John]

20 minutes ago, reezeh said:

Quite what is meant by window screen? Is it that stuff Americans put on their doors to keep bugs out of the house? What mesh size, if that matters?

I've seen one of these things and it was made of 3 layers of metal mesh overlapping in different directions with different aperture holes cut in them. I've not been able to actually try one, as yet. Here is a picture of one which I hope shows things better than I can describe them:

On the occulting bar, it needs to be right up against the field stop because it needs to be sharply defined in the field of view.

[Stu]

14 minutes ago, John said:

I've seen one of these things and it was made of 3 layers of metal mesh overlapping in different directions with different aperture holes cut in them. I've not been able to actually try one, as yet. Here is a picture of one which I hope shows things better than I can describe them:

On the occulting bar, it needs to be right up against the field stop because it needs to be sharply defined in the field of view.

Apodizing mask?

http://csastro.org/a-do-it-yourself-apodizing-mask/

Must try that out at some point.

EDIT sorry John, just seem your earlier post.

[Saganite]

12 hours ago, Demonperformer said:

Although I have never had any success myself, I have read that one thing that can help in finding the pup is to use a Y-mask lined up so that the diffraction spikes run N-S. This apparently reduces the glare of the star in the E-W direction. Although the pup is also diffracted, the effect is much less and so relatively it becomes easier to see. That's the theory, but, as I said, I've never had any success myself.

I will give that a try.

[mikeDnight]

2 hours ago, reezeh said:

Did you see anything worthwhile then, like help with any doubles? Even anecdotal recollections if you're happy to hit me with them.

Sorry Robert, i only used it that once to block out Alnitak while using a 6" achromat. It worked well but I was unsuccessful with the nebula at that time. I've since seen the Flame several times in my 100mm scope simply by keeping Alnitak out of the field, or using an H-beta filter. May be you could use a clear filter with a black spot in the centre to occult a bright star like Sirius. 

"Anecdotal Recollections" sounds like the title of a good book, and we could probably all play a part in authoring it!  My experiences with double stars is pretty limited, but I have had periods of enthusiasm towards them. I love a challenge, and enjoy pushing my scope to its limit in every regard. Uneven binaries can be particularly challenging and need steady seeing, and I prefer to use planetary eyepieces such as ortho's, plossls or short FL pseudo Masuyama's, rather than wide field eyepieces.  Binoviewers work well in double stars, perhaps because its often more comfortable to observe using both eyes. Or possibly because longer focallength eyepieces can be used in conjunction with a barlow in the bv, allowing reasonably high powers to be used effectively. Obviously, a barlow can be used with a mono eyepiece, but the advantage a barlow on a binoviewer, is that the increased separation between Barlow and field lens effectively doubles the power of the Barlow, so 2x becomes 4x ish! So cheap eyepieces can be used to great effect!! ☺

[John]

39 minutes ago, mikeDnight said:

...May be you could use a clear filter with a black spot in the centre to occult a bright star like Sirius....

 

That might work if the filter surface could be positioned close to the focal plane of the eyepiece so that there is a reasonable degree of sharpness of the obscuring spot. If the filter is in the usual place (eg: end of the eyepiece or end of the diagonal barrel) I think it's going to reduce the light but not really mask out Sirius ?

I've tried various filters on Sirius hoping to reduce the glare from the primary star to enable the secondary star to be seen more easily but so far the results have been that, while Sirius A is better defined with less glare, the faint Sirius B has been filtered out

[JTEC]

You might be interested in this extract from a note I made in early January when I was evaluating the new Burgess Supermono that was reviewed recently by Bill Paolini. The scope was a TEC 140. 

 ‘We had a rare clear night here in Surrey UK yesterday and I spent more time with the eyepiece (the Supermono) and a couple of others. Observing the Trapezium, nicely focused and centred in the TEC 140 at x98, the F and E stars pinged decisively into view. The most striking aspect was the relatively bright transmission rather than the precision of the view. Changing to a 9mm Tak Abbe ortho, x109, the view was better differentiated. The F and E stars were much more cleanly separated from C and A whereas, despite careful focusing, with the mono, their brightness tended to spill to reduce this separation. Perhaps in part a coating issue? Following on from this, the Tak gave very obviously clearer differentiation of magnitudes, with the F star, for example, in moments of good seeing, showing as a tiny pinprick of fainter light separated from C by clear dark space. The mono was slightly warmer in tone, to my eye. Even allowing for the difference in mag between the two eyepieces, I’d say that in this test the Tak proved to be the more refined performer, capable of showing finer distinctions spatially and in terms of contrast and brightness. That said, the mono is a very good performer on axis and is staying.’  

(Sorry about the massive font ... which now won’t go away ... I copied the note over from an email - I’ll add some more comments in a separate posting if anyone is interested.)

 

Font fixed - Stu