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Transform Campaign of 2017 includes Prizes!

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SGEO's picture
Transform Campaign of 2017 includes Prizes!

It's that time of year that our favorite calibration targets, M67 and NGC 3532, are conveniently in the evening sky. You all have heard how important it is to transform your photometric observations: it makes our data more valuable. So let's all do it! Take a look at the lead post in the past campaign forum thread : We have the tools and training materials to make this process accessible to all.

And... And we have a special incentive for observers to try their hand at transformation: participants will be entered in a raffle to win $500 generously donated by members of the AAVSO!

To become eligible:

1) Report your B and V band transform coefficients (Tv_bv and Tb_bv (eV and eB for you Pep guys cause you can play too) ), along with the method you used to determine them, to this forum.  Include the make/model of your OTA, filters, and camera.  If you already have coefficients in hand from June of 2016 or later, they are acceptable. And it doesn't have to be M67 that you use: M11, NGC 1252 and NGC 3532 in the South are now all available with reference data for your calibration.

2) Submit transformed B and V magnitude pairs acquired between today and May 15, 2017 (JD 2457889.0) for at least ten stars.  Data must be received in WebObs by May 31, 2017, local time.

Observers world-wide are eligible (a winner outside of the US will be paid with an international money order in US funds).

Good hunting!


tcalderw's picture
I'll go first

With my SSP5 photometer having Optec filters mounted on a C9.25:

eV= -0.066

eB = -0.008

and, for fun, k"B = -0.053


FJQ's picture
I'll go 2nd

M67 Transforms - C-11 @ F/6.0, SBIG ST-10xme Astrodon IVB filters (have R filter, but its an old Schuler glass filter with probable "hazing").  Performed instrumental magnitudes using Vphot from M67 data taken 30-Jan-17, reduced in Transform Generator V6.0.  These transforms coefficients are applied to my photometic variable observations using Transform Applier V2.49:


Tbv  1.469 +/- 0.032

Tb_bv 0.316 +/- 0.012

Tv_bv -0.002 +/- 0.014

Tri     1.018 +/- 0.026

Tv_vi -0.001 +/- 0.018

Ti_vi -0.031 +/- 0.024

The transform coefficient are changing very little from the one dozen or so I've taken over the last 3 years.  The biggest change comes from doing them from a remote dark sky site at 8000 foot elevation, but most of my data is taken at 400 foot elev, about 10 miles east of downtown Los Angeles!



hjw's picture

Meade 14" SCT/F10, SBIG STL-1001E. Custom Scientific B and V filters. Instrumental magnitudes using Vphot from NGC 7790 data taken Fall 2016 at the observatory ele. @9000 ft., reduced in Transform Generator V6.0. Transform coefficients are applied to my photometic variable observations using Transform Applier V2.48. I plan on doing another transform on M67 soon.

Tbv 1.307/error .0050

Tb_bv .1430 error .0100

Tv_bv -0.0770 error .0200



MMU's picture
Help with M67 in VPHOT

I'm trying to compute my transformation coefficients using two different techniques so that I can cross-check against each other. One technique uses VPHOT, but is there a "trick" to getting VPHOT to load the M67 standards sequence? I have a "normal" variable star field image loaded into VPHOT and click "Load AAVSO Comp Stars" and the comparison sequence loads for that star. I put an image of NGC 7790 into VPHOT and click "Load AAVSO Standard Stars" and the standards sequence loads for NGC 7790. I put an image of M67 into VPHOT and click "Load AAVSO Standard Stars" and I get an error message: "Comp stars/sequence exist, but none was imported due to no photometry for this particular filter, or too faint to be detected.0X17378DB". I'm using the same filter name for all the images ("V", although maybe with some trailing spaces).

What could I be doing wrong?

- Mark


MMU's picture
Re: Help with M67 in VPHOT

Never mind. I figured it out. It was a FITS keyword problem. (Turns out that the default units for CDELT1 and CDELT2 is deg/pixel, not arcsec/pixel as I had assumed. This caused VPHOT to calculate a totally outlandish field of view, which caused all kinds of problems.)

- Mark

MMU's picture

OTA = Meade LX200 10" SCT

Filters = BVRI from Astrodon

Camera = SBIG ST-9

Software: IRAF (appphot) + TG V5.10 (checked against VPHOT + TG V5.10, but got smaller residual errors with IRAF)

Field: M67, imaged on 12March2017

Tbv: 1.009 +/- 0.009

Tb_bv: 0.022 +/- 0.010

Tv_bv: 0.002 +/- 0.010

Tvr: 1.088 +/- 0.015

Tv_vr: 0.005 +/- 0.020

Tr_vr: -0.092 +/- 0.021

Tri: 0.939 +/- 0.019

Tr_ri: -0.116 +/- 0.025

Ti_ri: -0.038 +/- 0.026

Tvi: 1.009 +/- 0.010

Tv_vi: 0.001 +/- 0.011

Ti_vi: -0.012 +/- 0.011

Tr_vi: -0.052 +/- 0.011


- Mark

MZK's picture
Filters & Method

Hi Mark:

Could you clarify whether the filters are older colored glass filters or newer coated filters?

It would also be nice to see how the two software alternatives (IRAF and VPhot) compare. Could you provide the VPhot results also?



MMU's picture
Re: Filters & Method

The filters are coated and fairly new (2-1/2 years old?).

The transforms that I got using VPhot photometry are (these were from the exact same set of M67 images as I used with IRAF):

Tbv: 1.014 +/- 0.017

Tb_bv: 0.005 +/- 0.015

Tv_bv: -0.016 +/- 0.010

Tvr: 1.073 +/- 0.019

Tv_vr: -0.031 +/- 0.020

Tr_vr: -0.098 +/- 0.020

Tri: 0.942 +/- 0.027

Tr_ri: -0.117 +/- 0.023

Ti_ri: -0.075 +/- 0.033

Tvi: 1.011 +/- 0.016

Tv_vi: -0.019 +/- 0.011

Ti_vi: -0.029 +/- 0.014

Tr_vi: -0.053 +/- 0.010

The coefficients themselves match fairly well. The biggest difference is with Tv_vr which was +0.005 using IRAF photometry and -0.031 using VPHOT photometry.

- Mark


moont's picture
Transformation Coefficients from Down Under!

System: CMOS camera (ZWO ASI174MM), BVRI filters (mounted in Xagyl FW) attached to a SkyWatcher 150 mm f/5 Newtonian reflector. (Total cost ~ $2000)

Filters: B: Baader Johnson B filter (interference coating), 4 mm thick.

             V: Wratten #12 dye-in-glass cemented to a Schott BG39 dye-in-glass, total thickness ~ 3.5 mm

             R: Wratten #23A dye-in-glass cemented to a Schott KG3 dye-in-glass, total thickness ~ 3.5 mm

              I: Schott RG9 dye-in-glass, 3 mm thick

Standard stars measured: AAVSO standards in NGC 3532 and 1252 (plus a few Cousins E-region standards) on 2 photometric nights (suitable for all-sky photometry).

Average of measurements for 2 nights:

Tb_bv = -0.118

Tv_bv = -0.055

Tr_vr = -0.134

Ti_vi = 0.001

Tbv = 0.933

Tvr = 1.049

Tvi = 0.961

Ideally want T for magnitudes between -0.1 and 0.1 and T for colors between 0.9 and 1.1. Measurements suggest V and I filters are 'well-matched' while Baader Johnson blue filter ($200+) and bespoke R filter are not as 'well-matched'.




HBB's picture
BHarris Transformation Coefficients

My coefficients were obtained by imaging M67 on 3/16/2017.  OTA:  Meade 0.4M SCT @f/8.  Camera: FLI  Proline 1kx1k back-illuminated CCD chip.  Filters:  Astrodon BVRI.  Transformation Generator v6.0 used.


Barbara Harris (HBB)

jfgout's picture
M67 Transforms

This is my first try at calculating transformation coefficients. I hope I did everything correctly. My B-b vs B-V (and also V-v vs B-V) regressions are not nearly as good as what is shown in the examples (Fig 6.5 of CCD photometry guide : Is this normal? Everything else looks fine (with nice linear regressions between my instrumental magnitudes and the standard values).


Anyways, treatement and photometric analysis was done with IRIS, on 13 stars in the M67 field (mostly stars outside the cluster because of my low resolution).

Setup: Atik 414ex on Orion ED80 (80/480 refracting scope). Filters: Astrodon Photometrics UBVRcIc (almsot brand new, I bought these in December 2016).

All images were taken on March 16, between 02:10am and 02:45am UTC from Bloomington, IN (USA) in a heavely light-polluted environment. 30 to 75 images per filter processed and stacked with IRIS.










If I have another clear night by APril 15th I'll try to do the same for my C8 and maybe also try to replicate the results with the ED80 and compute some average values across two independent measures.


ldj's picture
Transform of Planewave CDK24/Apogee CG16M/Astrodon Filters

Thanks for the encouragement to (finally) do this. Below are the results for the Burke-Gaffney Observatory (Nova Scotia) based on one observation set taken on March 12. I'll run it again soon to see how consistent it is.

The TG program was easy to figure out and use - thanks to the developers. I did the photometry in MaxIm. I dropped outlier stars 14, 30 (i issues), 38 and 51 (stars close together).

Any comments on how this transform looks are welcome!  

[R Squared Values]

Tbv= 1.023
Tbv= 0.006
Tbv= 0.999

Tb_bv= -0.005
Tb_bv= 0.006
Tb_bv= 0.021

Tv_bv= -0.028
Tv_bv= 0.005
Tv_bv= 0.471

Tvr= 1.031
Tvr= 0.009
Tvr= 0.997

Tv_vr= -0.056
Tv_vr= 0.009
Tv_vr= 0.466

Tr_vr= -0.086
Tr_vr= 0.011
Tr_vr= 0.604

Tri= 0.971
Tri= 0.014
Tri= 0.992

Tr_ri= -0.103
Tr_ri= 0.013
Tr_ri= 0.595

Ti_ri= -0.073
Ti_ri= 0.019
Ti_ri= 0.251

Tvi= 1.002
Tvi= 0.008
Tvi= 0.997

Tv_vi= -0.030
Tv_vi= 0.005
Tv_vi= 0.454

Ti_vi= -0.032
Ti_vi= 0.009
Ti_vi= 0.236

Tr_vi= -0.047
Tr_vi= 0.006
Tr_vi= 0.601

Cheers, Dave


TRE's picture
Throw it in the hat

here are my M67 averaged coefficients from TA. Images from 12-16-16

ObsLon=-88 32 43
ObsLat=41 44 41

WebOBS shows 20 AAVSO variables, all one~20' field, ranging from 8m to 13m with skimpy errors taken from VPHOT on JD-2457830. Most are sparse in the AAVSO DB.   VPHOT averages of 5 or 6 mug shots at A.M.~1.6. Not ideal but most are usable.

Gobs more to come if I can find time to reduce and transform it all.

VPHOT, TG, TA all very useable. MaxIm DL for imaging, solving, and image calibration. OTA is old Meade 8" SCT. Camera is used (shutter has >>500,000 openings) ST8XME.  BVI filters are Custom Scientifics. All images visually inspected.


Another set from downunder

Also using NGC 3532 (thank you for providing) which is nice and high around midnight at the moment at 32° south.

Image train - DSI RC14C telescope, Astrodon B & V filters and a [very old} SBIG ST-10.

21 stars run through MaxIM DL, and using TG Version 6 - a positively luxurious experience compared to using the old manual spreadsheet method. Thank you developer(s).

Tbv = 1.016
Tb_bv = 0.028
Tv_bv = 0.012


PS - quick question. Does TG average multiple data automatically? Ie, in my case 5 x 3 second V images plus 5 x 8 second B images in my CSV file.


mgw's picture


Yes, TG automatically averages multiple measurements of each star.


hjw's picture
Transforms with ensemble measurements

I've noticed some of you like DKS have been succesfull 

Doing transforms with ensemble measurements. I've heard this is tricky, but how is it accomplished?

spp's picture
Transforming ensemble measurements using VPhot

In VPhot:  You must first enter your transforms in the Admin>telescope setup section.  You must also have a "saved" comp star sequence for the target. .  In most cases you would use the AAVSO comp star sequence for the target, but you must save and name the sequence in the image display for one of the images.  

First load one of your images.  From the Catalogs box load the VSX stars and also the AAVSO comp star sequence.   Name and save this sequence from the small box at the upper left of the image display.  Your saved sequence must include the target and (I believe) a check star.  You then go back to the images list.

Let's say you have transforms for B-V.  From the images list, click in the selection boxes for the B and V images of the photometry ensemble images you want transformed.  Then, from the menu options, just above the images list, click "transform".   In the first "Color photometry" page, select the name of the sequence you saved for this target.   The next page will show the transformed B and V magnitudes for your target(s) and the check star.


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