I expect a number of new PEP observers to become active in the coming months and they will likely have common questions to ask and experiences to report. We’ll use this thread as a container for those communications.
Tom
First thing: new observers will need an AAVSO online account and an Observer Code. It is also greatly encouraged and appreciated to become an AAVSO member. See the link below. Tom
Where can one purchase a PEP?
Peter
BPEC
Peter:
Optec no longer sells these photometers. I scrounge used ones to loan out.
Tom
I’m signed up now, observer code CMIM. The PEP is somewhere over the Pacific Ocean.
By way of introduction I am an amateur astronomer in Auckland, New Zealand. My main interest is Asteroid Occultations. I responded to Tom’s call for southern hemisphere observers and am well positioned for Antares observations.
Michael
First Steps
New PEP observers will need to get the photometer mounted on the telescope. This may require balance adjustments, for the SSP is heavy. If you have a cassegrain scope on a fork mount you will need an equatorial wedge. In alt-azimuth mode the optical tube can only be brought up to about 65 degrees altitude before the photometer case hits the base of the fork.
With the mechanical installation done, you will need to work out the best way to run the 12V power cord so that it reaches the photometer in any orientation. When operating the scope be careful not to start wrapping the cord around the mount.
With that done you are ready to start experimenting with the photometer. Try centering it on a star and see how well your mount keeps it in place. This may differ in different parts of the sky.
Next, get a handle on how far you must move the scope off-target to take sky readings. An easy way to do this is to set the integration time to one second, and with a slow slew speed move away from the star until you see the counts stop dropping. Flip the mirror and look in the eyepiece to see how far you have moved. The brighter the star, the further you must go.
At this point you should look at chapter one of the PEP observers guide (Photoelectric Photometry (PEP) Observer's Guide | aavso)
Try a single-filter sequence on one of the PEP program stars. At this time of year (May-June) you could try one of the “constant” targets, SY UMa or NSV 6687 (UMi), with V magnitudes given below. The complete target list is found in the “starparm” file (Photoelectric Targets and Data Reduction | aavso).
SY UMa 5.28, comp HD 82328 3.175, check HD 82621
NSV 6687 4.275, comp HD 136726 5.013, check HD 142105
Until you have established color calibration you will not be able to submit results - right now you are just trying to become comfortable with the steps of the sequence.
As you proceed with the sequence watch the counts. Those numbers are your best diagnostic of trouble. The counts should be fairly consistent during the sequence. It’s a particularly good idea to fix in your mind the approximate count for the first sample (comparison star) and see that subsequent comparison counts are comparable.
And I forgot to add: give your photometer time to acclimate to the outdoor temperature - at least half an hour (I try to allow 60 minutes), and let the electronics run for at least ten minutes. As the ambient temperature changes, your counts will change and this will be most apparent in the sky readings or when you have the mirror down for eyepiece viewing.
If you habve a Generation I photometer, there is a mechanically adjustable “offset” that governs how many counts take place with the mirror flipped down. A few hundred counts in ten seconds is appropriate. [The Generation II offset is harder to adjust.]
Tom