Starship Asterisk*

I now think the above analysis is NOT the best way to do photometry with NSL data. I have been working with photometry files very closely over the past few weeks and my thoughts are continually changing. They have returned to something I have belived previously and even posted recently. (See thread ...

First light for the Cerro Pachon CONCAM! http://nightskylive.net/cp/cp040917/cp040917ut094330p.jpg The above image is not as spectacular as the recent first light from the Haleakala CONCAM and so we are trying to figure out why. My first guess is that the fisheye lens iris is not very open. Now this...

I have been trying to understand why Polaris from CI has been jumping around so much recently and so I decided to check to see whether CI observatory itself has any independant information about variable extinction on their web pages. And they do! Saharan dust has been having a big effect on recent ...

The NASA APOD site is currently not responding. I notice that main NASA Goddard Space Flight Center site http://www.gsfc.nasa.gov/ is also not responding, so I would guess there is a general problem with connectivity at NASA's GSFC. I would expect that this would be solved soon after the system peop...

Most of the time the water drops shown on the lens just evaporate, if not during the same night then in the Sun during the next day. If water on or in the lens remains a problem for HL, then I would recommend first heating the lens. This should reduce the time that it takes for water spots to evapor...

The NASA APOD is down today due to a power upgrade in Building 2 at NASA Goddard Space Flight Center. The NASA APOD should return by later today (Sunday) and Monday should not be affected at all.
-RJN

Tilvi, Yes, your plot shows the same thing! Very good. I have been thinking about whether this is caused by pixel sensitivity or "top count pixelization". I think I have new data that can show that the later is more important. CI recently had a frame where a cloud covered Polaris. The (FIT...

I have been playing with Polaris data trying to get a reasonable light curve and this has led me back into an investigation of a well-known type of systematic error that affects the type of photometry that is automatically computed and recorded. It is easy to note that the C1-B values for Polaris (A...

The strange frames are caused by our software during the switch-over from 180 second integrations during no-Moon, to 20 second integrations when the Moon is above the horizon. What happens is that the old 180-second dark frame is being used during the first few 20-second integrations. A new dark fra...

The new HL CONCAM3 is returning excellent images last night for the first time. Last night one of them (at least) shows a streak that I am trying to identify. Here is it is: http://nightskylive.net/hl/hl040910/hl040910ut084817p.jpg Note that the image is really upsidedown but I am sure that will be ...

Two more strange CI images with unknown streaks. One followed the other by about 25 minutes. Here they are: http://nightskylive.net/ci/ci040908/ci040908ut051126p.jpg and http://nightskylive.net/ci/ci040908/ci040908ut053507p.jpg The brightness of the left is just the Moon. The streaks are better seen...

Thanks (again) Joan. We'll consider it. - RJN

Thanks, Joan. Fixed it. -RJN

The Kitt Peak CONCAM went down for an undetermined reason a few nights ago. Our KP site coordinator, Mike Hawes, has been alerted and emails us that the CONCAM computer appears to respond normally to being rebooted. We therefore expect normal operations to begin again tonight after the (new) sunset ...

Here is an idea that appears to get rid of both vignetting and atmospheric absorption effects in the photometry. For a comparison star, use the SAME star on the previous night. Take the ratio of photometric values on the two nights at the same SIDEREAL time, not the same SOLAR time. At the same side...

I have been investigating methods of doing photometry when there are no good comparison stars within a few degrees. In these cases a star will appear to fade as it sets and there is no good way to correct for it (as yet). It is therefore hard to tell if the star has short term variability. I was pla...

I like the SF method. It might have problems near the poles, though, as stars don't move so much there and a single star might dominate the entire night. Like Polaris, for example. Anway we might try several of these ideas out in a "flat frame Olympics" and see what works best in practice....

Any ideas? Airplanes?

Tilvi, It is really good that you are studying flat-fielding and the link you gave was excellent. We should use the information there as a base for what we do for flat-fielding future CONCAM images. I agree that flat-fielding will reduce the systematic errors on CONCAM images. I think we have alread...

Tilvi, Interesting plots! I think pixel sensitivity is combined there with the stars' point spread function (PSF) spreading out onto the five brightest pixels in a different way. Theoretically, each of the pixels could be uniformly sensitive and still C5 would change as the star's PSF moves across t...

Thanks, Noah! Interesting. While chasing your links I chanced across this PASP paper: http://adsbit.harvard.edu/cgi-bin/nph-iarticle_query?bibcode=1984PASP...96..366G that is also interesting. I think Betelgeuse would make a good NSL project for a student. NSL data gives the most continuous and most...

I recalled that Betelgeuse (Alpha Ori) was quite variable so I wanted to check this with archival NSL data. The first bad news is that Betelgeuse saturates the 65K ceiling of the CCD chip, as shown by CI C1-B counts above 60K at many times. We have learned not to trust saturated data, even for C25. ...

A quick look at zeta Aql over a 3-hour stretch shows no clear variability where, quite possible, a variability of 0.2 magnitudes of more would have been clearly evident. This is for CI data on 2004 August 17 with Alpha Aql (Atair) as the comparison star. Somebody should go back and do this better, b...

The list of 25 brightest stars indicates that Altair, alpha Aql, is constant. So I decided to check NSL data with this. I decided to take the ratio of gamma Aql to alpha Aql as both were WOLFed to automated photometry files from CI on 2004 August 17 (and many other nights). I first window copied the...

There are some very small spots that have been appearing recently all over CONCAM images from the Canary Islands (CI). The latest image (as of this post) shows these, especially near the edge of the sky-illuminated circle: http://nightskylive.net/ci/ci040904/ci040904ut055846p.jpg The movie files sho...