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R CrB images from the new BSM_NM system

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spp
spp's picture
R CrB images from the new BSM_NM system

I just looked at my first set of R CrB images from the new BSM_NM system.  Wow!  They are beautiful,  still with a nice large FOV's but with better SNR's for fainter comps.  There are a couple of wrinkles. 

Wrinkle 1:  It seems the target is saturated in the V and B images. 

In the B image, VPhot displays the target as non-linear (greyed out).  The maximum pixel value inside the measuring aperature is shown as 62,041 ADU's.

In the V image the target is also displayed as grey, non-linear.  The maximum pixel value inside the measuring aperture is shown as 62389 ADU's.

In the I image the target is displayed as green.  The maximun pixel value inside the measuring aperture is 37,240 ADU's.  In the I image the target is not saturated.

This situation may be complicated by something I did by mistake.

Problem 2:  When I first saw this data set in my VPhot Available Images window the Telescope (Tel) column showed these image were from "ACP->E180_ASI183_ParamountME".  I didn't recognize this system, so I looked in the header and saw it was from BSM_NM.    I rashly "renamed" the Tel identification of all the images to BSM_NM.  Big mistake.  I think VPhot is now using the telesocpe information from the original BSM_NM system.  

I tried "renaming" the Tel column back to the original  "ACP->E180_ASI183, etc.", but VPhot wouldn't let me do it.   Regardless of this, these images are not usable since the target is saturated.

For problem 1:   I recommend that the exposure times for the B and V images be shortened to prevent saturaton of the target, perhaps to 15 seconds for B,  and 7-8 seconds for V.  That said, I would not like to see a drop in the SNR's for the fainter comps in this field,  The fainter comps are better quality (mostly SRO) than the brighter comps (mostly Tycho-2 and TASS). 

To keep the SNR's up for the fainter comps, I'd recommend increasing the number of exposures in the B and V images.  I think seven to eight 15 sec exposures for B, and four or five 7-8 sec exposures for V would work.  I think the I image settings are okay (unless 37K ADU's is over the linearity limit for the new camera.)

For problem 2:  I think it would help users of this system if you gave it a new, more conventional, VPhot Telescope name (like BSM-NM2).

I am eager to see another set of R CrB images from this new system.   I think there will be a significant improvement in the photometry when I am able to use more of the better quality, fainter comps in this field. 

Phil

HQA
HQA's picture
new BSM_NM

Hi Phil,

I'm glad that you like the new setup for BSM_NM!  This is the second BSM with the E-180 astrograph.  The third will be BSM_NH2, with that upgrade to take place in April.

As for exposures: there will be a short period where we make adjustments to compensate for the larger aperture, higher QE camera and better seeing at NM.  I'll give your requests to George Silvis, who is getting the queues up and running for the new setup.

Arne

SGEO
SGEO's picture
R CrB on BSM_NM

Phil,

I made the exposure adjustments as you specified

The telescope naming is still being sorted out. The observatory is BSM_NM but the telescope (FITS key TELESCOP) should be BSM_NM2.  You will find two telescope profiles setup for the old and new setup. I'm still trying to figure out who sets the TELESCOP value, Maxim, Sky or ACP.

George

 

spp
spp's picture
R CrB on BSM_NM(2)

George,

Thanks for making those changes. 

I have never figured out the preferred method of communicating with the BSM team with feedback about the images.  Is posting feedback in this forum okay?

I just got the second set of R CrB images.  Again, the images are beautiful.  The tracking looks perfect and I don't detect any evidence of vignetting in these calibrated images (...showing very flat vertical and horizonal profiles even in the corners).  I'm wondering if the camera field is fully illuminated, or if the flat is correcting out some vignetting.

There is one problem with this latest set of image for 2020-03-15:  The pointing is off a bit.  (see screenshot).  All of my comp sequence is still there, but too close to the edge for comfort.  In the first set of images for 2020-03-05 the targets and comps were nicely centered.

I don't know if this is possible with the current system for controlling the mount, but the Paramounts using TheSkyX control can be set to use a "closed loop slew".  This centers the target to within a very few pixels every time, even if the T-point model pointing by itself is offset significantly.  The closed loop slew requires only an additional 10 or 15 seconds

Phil

 

 

 

spp
spp's picture
BSM_NM2 transforms

George,

The second revision of the BSM_NM2 (E178) exposure settings for R CrB work very well.   I'll now be able to report magnitudes for both variables in that field (R CrB and TT CrB) in all the filters, and the best of the comps now have good SNR's.   Many thanks for putting up with my quibbling about the settings.

The BSM_NM2 telescope account still doesn't have transforms. 

I'll be happy to calculate the transforms for BSM_NM2 if you can get me BVI or BVRI images of M67 using the same exposures and numbers of images used for R CrB.  M67 is now in good position in the early evening..

Phil

 

 

MZK
MZK's picture
NM2 Transforms

Phil:

I have M67 images from NM2 but they are too faint. The plan has been revised but I don't have the images yet. I should be able to generate coeffs soon?

Ken

spp
spp's picture
NM2 Transforms

Ken,

I'd be more than happy to calculate the transforms when the images are available and give you more time for the many other things you have to do.  You could consider them "interim" transforms until you got around to doing the official transforms.  I am itching to get going on those images from the E178.

...but hey, no pressure.

                               Phil

MZK
MZK's picture
Transforms

Phil:

I just shared NM M67 images with you. Have fun! 

Ken

spp
spp's picture
Transforms

Thanks, Ken.

I stacked the images for each filter.  Every stacked image shows good SNR's in all the standard stars I use.  Nothing important was saturated.  

Transforms comming up.

Phil 

  

spp
spp's picture
Transforms for BSM_NM

Ken,

I just emailed the transforms to your gmail address.

Phil

HQA
HQA's picture
pointing

Hi Phil,

Unclear to me what you are trying to show with that screen shot.  In any case, don't worry about it on these early nights.  I redid the pointing model on March 26 UT, which should be accurate to 26 arcsec anywhere in the sky.  Not sure how to do closed loop slew without imaging feedback, but if you still feel the pointing is not good enough after the 26th, I'll look into it.

The forum is fine for communicating for now.  The nice thing about the forum is that asking questions shows activity, always a good thing!  Plus, some of your questions or issues may be common for other researchers.  The plan was for a "proposal advocate" to be assigned, who would then be an immediate contact person, but we haven't gotten that far along.

Arne

spp
spp's picture
pointing

Arne,

The intent of the screen shot was to show that the targets (R CrB and TT CrB) with the comp sequence stars are clustered in the right lower (NE) quadrant of the image.  Star 106 is quite close to the edge of the image.  If you look at the zoom box at the lower left you can see a diagram of the image which shows more clearly  the positions of the stars.  In the previous set of images these were all centered in the image.

Closed loop slew:  Yes, this is done using another image.  First the scope points to where the T-point model thinks the target should be, then takes an image.  That image is solved.  TSX then repoints using that solution to place the targert exactly in the center of the field. 

This sounds like it take a lot of time, but it really is done very quickly and automatically without any further instructions beyond "Closed Loop Slew".  I'd say it takes an extra 15 seconds or less.

Phil

spp
spp's picture
latest BSM_NM2 images

George,

I just got the latest batch of R CrB images with the exposure adjustments.  Unfortunately, the adjustments were too large, and the SNR's in all the stars are too low. 

The recommendations were 15 sec for B, and 7-8 sec for V, but they are now set at 10 sec for B, and 5 sec for V.  Even with the increased number of images the signals are now too low.  Could you please try again setting the exposure times:  B   15 sec,    V   8 sec.   After seeing the effect of halving the exposures times, I think 15 sec and 8 second should be much closer to the mark (decent SNR's in the best comps without saturating the targets).

Progress:  These latest images now show "BSM_NM2" in the "Tel" column of the Available Images page.  Am I correct in thinking that the "Tel" column reflects the value of the header's keyword TELESCOP?

I looked in the list of telescope systems in Admin>Telescope Setup.  As you had mentioned, there are two systems with the Display Name of BSM_NM.  The second has a TELESCOP name of BSM_NH2.  I looked at the information in the BSM_NH2 system.  I found no color transforms in this system's profile.  Are these transforms available, at least for B-V and V-I?

I'm sure you have a lot of other things to do, and I really appreciate your work on this.  I hope all this will provide good experience for learning how to get the best from these new telescopes.

Phil

Monday, Mar. 30  I just corrected an error in the title of this post.  BSM_NH2 was corrected to BSM_NM2.

Phil

 

 

 

spp
spp's picture
Thanks, George

Please see post #5.

HQA
HQA's picture
BSM_NM2 etc.

We've figured out why autofocus was not working on BSM_NM2 (thanks, Helmar!), so images from 4/9 onwards are properly focused at V.  I need to take an hour and calculate the deltafocus offsets between filters.  They are pretty parfocal, but I think I can improve the focus for other filters.

That said, on 4/9 the images are in the 2 pixels per fwhm range, just about right for photometry.  However, that means recorded seeing is in the 4arcsec range, which is worse than Bill Stein's site can produce.  So I am betting that, somewhere in the near future, we will have to revert back to 1x1 binning in order to remain properly sampled.  That would mean images would increase in size from the current 5Mpix to 20Mpix.

The faint halo you see around stars is most likely a reflection off of some optical surface, such as within the E180 corrector or the top/bottom surfaces of the filter.  If you do a profile plot of a star, you will see that this halo is very faint and should not affect the photometry.  I've often seen similar haloes on other telescopes when using narrow-band filters like Halpha.  BSM_Hamren, the other system currently using the E180, doesn't seem to have these haloes, so I need to compare optical layouts of the two systems to see if there is something obvious going on.  The seeing at Hamren is worse, and so that might be obscuring underlying haloes.

BSM_Hamren's cloud sensor (actually, the rain sensor module of the unit) is not working and is being sent back to the vendor for repair.  This system will continue to operate, but may be restricted to clear nights without rain possibility.  We have a different model cloud/rain sensor and will be testing it soon.  Thanks to Gary Walker's machining expertise, I have new mounting plates for BSM_NH2, and I'm hoping to start the install of the BSM_NH2 E180 this week.  That will give a third system for comparison.

These E180 systems give superior images and enable the BSM network to go much fainter than before.  If you have a 13-14th magnitude target, we can get good data.  I'll do some tests after the moon fades and see how faint we can go with reasonable (say 5min) exposures.  That said, we have a slightly smaller field of view (1.5x1.0 degrees) than with the older refractors (1.9x1.3 degrees).

Arne

spp
spp's picture
Images from BSM_NM2, BSM_NH2, BSM_Hamren

Now that BSM_NM2 has transforms in VPhot I've started going through the large backlog of R CrB  images from NM2,  starting with the most recent and going backward in time.  The images are very good, and the current exposure settings work quite well for the R CrB field targets and comps.  The weather must be pretty good in New Mexico now, since I'm getting images from NM2 almost every day.

I am also getting occasional BSM_NH2 images which I am happy to get, and report the results when they don't duplicate data from NM2 on the same date. 

Today I also received images of R CrB from a telescope named "ACP->Driver for telescope connected through TheSky".  A check of the header showed this is BSM_Hanrem.  A look at the images showed this was from one of the new E-180 telescopes. 

I won't be able to report the photometry on this image set for two reasons:  WebObs doesn't recognize  "ACP->Driver for telescope connected through TheSky" as a telescope, and I have already reported R CrB data from one of the other telescope for the same date.

If  the AAVSOnet team would like reports on image quality, focus, pointing, exposure times, etc. for this new system I'm happy to oblige, but I don't think I can handle more regular data for R CrB from a third system.

I have attached a screen shot of a portion of VPhot Photometry Report for the Hamren stacked V image (10s X 9).  R CrB was saturated, as was the brightest comp star (74).

Phil

spp
spp's picture
test exposures for BSM-NM

Today I found two images for R CrB in my list, a 5s B and a 2s V.  These exposures are good for the R CrB field, neither target saturated and pretty good SNR's in the comps.  I would expect a 2s exposure for Ic would also work.  Please switch my  R CrB images to these new exposures.

Thnaks

Phil

MZK
MZK's picture
R CrB Exposures

Exposures changed as requested.

Ken

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