Dave Smith

39 minutes ago, Davey-T said:

I had one that the light turned green when indoors in the warm but as soon as I took it outside it turned red again.

Dave

When I took mine outside today it stayed green but the clouds became rather threatening so all is packed up again.

Dave

Thanks for all the helpful comments and also the link to SolarChat. I tried plugging it in again and the light was still amber after half an hour and no sign of any warming up.

 So I brought in indoors while having a late breakfast. I left it plugged in and to my surprise found the light was green and the red section felt a nice cosy warm. I then turned the dial and it has since returned to green.

So I am now desperate to try it on the scope with the Sun but, of course, it is cloudy.

To answer earlier questions, the disc of the Sun did look featureless apart from sunspots and before this there had been no degradation of the image.

I will report back once I am able to get a glimpse of the Sun. 

7 hours ago, Davey-T said:

Does the LED change from red to green ?

Dave

Hi Dave, I'm not too sure about that. Thefirst time it stopped working it didn't change to green. When I  next tried it was a lovely green and I hoped it would then work but alas not. I did try again but not really green.

Dave

I have used my Quark successfully for a few years but it has suddenly stopped tuning to see in H-alpha. Nothing has changed in my setup and I am using the same battery as ever. The light comes on but the view as seen by my camera only gives the white light view. After 10 minutes plus there is no change.

Has any one experienced this before? It looks terminal to me.

I suspect it has gone into a big sulk because behind it's back I have ordered a Lunt 60mm !

I would be grateful for any ideas.

Dave

I use an Atik 460Ex with a photometric V filter. I am sure however many CCD cameras would be suitable. One consideration would be the field of view to ensure enough comparison stars  are in view. My main interest was once imaging so I do have a filter wheel with sufficient places to take  LRGB and Ha,O3,S2 as well as the V.  You can screw a single filter onto the end of a CCD camera so a filter wheel is not essential.

I used to use an Atik 314 Both Atiks are low noise and I find it only necessary to cool to -10 degC .  The chip of the 460 is double the size of the 314. By the way it is not essential that yoou but a V filter straight away. Useful work can be done unfiltered. It is worth getting one once hooked. They are not cheap.

I hope that helps a little.

Dave

2 hours ago, woodblock said:

Hi Dave, the reason for picking a star with a long period was an attempt to check my method. I figured if I did a series of images and analysed them they should not show much variation in magnitude. If there was a significant variation then I must be doing something wrong.

I found it quite difficult to adjust the amount of defocussing. If you over do it the stars turn into circles.  I did find that some of the bright comparison stars were saturated so I'll have to adjust the exposure. The problem then is that the dimmer comparison stars you can hardly see to select them.

Thanks

STeve

 

Hi Steve

It is better if the comparison stars are of similar magnitude to the target star if possible.  I've just had a look at the aavso chart for S Cas and can see that it could be tricky. One of the brighter comparison stars have a few faint ones very close by.

Dave

Hi Steve

The purpose of defocusing is to help insure that the star image, and the comparison stars are not saturated. I don't go out of my way to defocus but don't worry too much about being in focus. It is important that you check that it is not too close to saturation.

S Cas has a very long period, you may find it more interesting to try a star with a short period so that you can detect change. Ther are suggestions on the BAA VS  web site.

Dave

What mikeDnight has said is very relevant, You can alternatively study eclipsing binaries which have a regular periodic pattern so that you can get the full picture over a number of nights.

I have mostly been looking at HADS stars that have a cycle of only a few hours and so it is possible to get one or more complete cycles in one session.

See here for ideas https://docs.google.com/spreadsheets/d/1oGA2HaEHE8L6eX19ZoHqQQTu0LYV56HX3Srg7oCtOHo/edit?hl=en&hl=en#gid=883500896

Dave

22 minutes ago, 7170 said:

@Dave Smith, many thanks for taking the time to write your tutorial! Nice to see others using AstroImageJ, its still my goto tool after many years.

A quick question, is there any benefit to stacking subs or not for variable work - what is commonly done? I must confess I've always calibrated, then stacked using average to create a new file. And then compared sequences of those new average files over time. Maybe I've been adding extra steps unnecessarily, as it is quite a bit of extra work.

I've never done that as the stars i have been looking at vary quite rapidly. I was advised that for longer period variations to just submit the individual readings. 

Dave

Hi Steve,

I don't  use that method at all. I get the comparison stars from aavso.  If that doesn't  work I  get comparison stars from a star chart program "Guide" which has the UCAC3 star database. Usually the charts from aavso are sufficient. Personally I  don't  put the magnitudes in at the AstroImageJ stage but later when putting the data into the BAA spreadsheet

Hope that helps.

Dave

Hi Steve. With SGPro it slews to where it thinks it should but then takes an image, plate solves it and then makes a correction. It will do this until target is in the centre as accurately as you choose.

Dave

20 minutes ago, woodblock said:

Thanks Dave,

The biggest problem I have at the start is in getting my telescope to point at the right place - but I'm working on that.

Steve

 

I find that the plate solving facility in SGPro brilliant for getting the star right in the middle of the FOV.

Dave

Each point comes from one image. No stacking involved. Each image has to have darks and flats applied before any analysis. This can also be done in AIJ.

Hooe that helps.

Dave

For a number of reasons I haven't been able to do any observing since the spring. Recently I did get out but unfortunately my scope would not go to the correct part of the sky. My target was just to the left of Mars but the scope kept on going to the right of Mars. It subsequently dawned on me what the problem was. My laptop had not done its usual automatic changing the clock to GMT. Once corrected all was fine. Since then I did have one evening where the results were rubbish and finally two successful nights. I had chosen stars in Cepheus to avoid interference from the Moon.

The gap in the data was due to cloud.

Dave

3 hours ago, woodblock said:

Hi Dave, I don't quite understand why you need to carry out Plate Solving on the images. 

Cheers

Steve

 

You don't have to but it makes the analysis run very smoothly.  With my images there is a small drift and so I  have to make a small correction about every half hour to an hour and unless it is done manually the program will lose the star.

Dave

12 minutes ago, woodblock said:

This is an excellent tutorial Dave, I haven't done any variable star observation yet but I intend to. I'm just collecting information at the moment. The AAVSO web site is very good and I'm working my way through some of their documents.  I think I have all the necessary hardware to start. 

I was wondering if it would be useful initially to carry out some photometry work on non-variable stars in order to check I'm doing it right.

Cheers 

Steve

 

Thanks Steve. You could do that but it would be just as easy and more rewarding to choose a known variable and see some variation that you know should be there.  What scope are you intending to use?

Dave

An excellent find Michael. Adding them to the BAA database could be very valuable.

Dave

Thank you all for your very nice comments.  Roger has been my BAA mentor and I owe him many thanks for the guidance he has given me. Early on he introduced me to the HADS project run by Patrick Wils. I subsequently met Patrick at the AAVSO/BAA meeting in 2018 and have enjoyed participating ever since.

Dave

1 minute ago, andrew s said:

It happens even if to the best.

Regards Andrew 

 

I have no excuse as this isn't the first time!

Dave

HADS star V417 Bootes. The large gap in readings was due to a technical error. i.e. I hadn't realised that the star was going to get so high in the sky and so the scope was gradually being covered by the dome roof. I interpreted the gradual fading of the stars as cloud but when I went out to shut down realised it was still perfectly clear. When I moved the dome back all was then fine so I started again - Duh !!!

We live and learn.

Dave

5 minutes ago, andrew s said:

Are you after some record ir another?  Great work. Interesting lumps and bumps do you know why? Not an area I have looked into.

Regards Andrew 

No record, just keeping myself occupied during this crisis. I cannot go out for anything else. If the sky is clear then why not?!!

The lumps and bumps are due to to it being multi-periodic.  If you add two (or more) regular curves of different frequencies together you can get shapes like this.

By the way, did you attend the BAAVSS - AAVSO meeting in 2018 and sit in the middle of the second row in the group photo, then you are next to me with Jeremy on my other side?

Dave

Another clear night and so another HADS star

Dave

Two clear nights - two more HADS stars.

Dave

Last night. 60 x 60s exposures.

Dave

Very nice.

Dave