Free course

Astronomy with an online telescope

The standard view of this forum does not always work well with assistive technology. We also provide a simpler view, which still contains all features. Switch to simple view.

You need to be enrolled on this OpenLearn unit before you can participate in this forum. Enrol now.

Picture of Rebecca McManus

Rebecca McManus Post 1

20 Dec 2020, 16:05

Matching finder chart and COAST image


I'm on the final week of the course and am having real difficulty matching my COAST images up to the finder chart (I've imaged EW2). I've looked at all of the images I took in all of the orientations the editor will let me and I just can't even match up the brightest stars in the image, let alone find the target or reference ones!

Do you have any advice / possible explanations as to why this may be or any tips? 

Thanks in advance, 


Picture of Dennis Ramirez

Dennis Ramirez Post 2 (summarised) in reply to 1

20 Dec 2020, 19:26
I had the same problem with that star, what I done is very simple, I put a...
 [Expand all posts]
Picture of Alan Cayless

Alan Cayless Post 3 (summarised) in reply to 1

21 Dec 2020, 14:02
Hi Becky; Thanks for asking about this - and Dennis, thank you for your reply...
 [Expand all posts]
Picture of Rebecca McManus

Rebecca McManus Post 4 in reply to 3

24 Dec 2020, 14:30 Edited by the author on 24 Dec 2020, 14:30

Hi Alan,

Thanks so much for your reply! I've had no joy using either Dennis' method or the one you've suggested - so I've requested a new set of images from COAST and will try again when they come through, hopefully with more success! 

Thanks again, and Merry Christmas!


Picture of Sarah Toney

Sarah Toney Post 5 (unread) in reply to 4

30 Dec 2020, 19:11

Hi Becky,

I am having the exact same problem with some images of EW2 I took in December. Despite following Alan's tips I have had no luck matching the images. There are no patterns of stars that are the same in both images. I think I will follow your lead and re-request images of a different star. Frustrating as it took weeks for these images to come back. 

Just wanted to let you know it's not you :)

Picture of Alan Cayless

Alan Cayless Post 6 (unread) in reply to 5

4 Jan 2021, 17:14

Hi Becky, Sarah;

Thanks for your patience with this, and sorry you aren't having much luck matching the images up.

If you could let me know a couple of the image reference numbers (usually a six-digit serial number starting with a "J") I'll check them out and see if we can figure out what's going on.


Picture of Sarah Toney

Sarah Toney Post 7 (unread) in reply to 6

4 Jan 2021, 19:08

Hi Alan,

Don't worry. It's a bit annoying but I'm still very happy to be doing a great free course so no major drama :)

My numbers were J368101, J368286, J368287, J368474

There just aren't any strong patterns that I can see.  I haven't been able to request images of a different area until tonight what with the technical problems. I have now requested some images of EW1 so we'll see if they're easier to match. 



Picture of Alan Cayless

Alan Cayless Post 8 (unread) in reply to 7

6 Jan 2021, 12:31 Edited by the author on 6 Jan 2021, 12:35

Hi Sarah;

Thanks for the image numbers - that has made it much easier to see what's going on. Your first image (J368101) is a bit fuzzy so I'd disregard that one, but the other three are quite useable.

Your images are indeed of the correct region of sky, and they are the same way round as the finder chart, so there's no flipping required in this case.  One thing to notice though is that the telescope images cover a smaller part of the sky than the finder chart, so the thing to do is to concentrate on the central area of the finder (I've marked this on the attached finder chart - small version below and full size version attached).

You are right that there aren't many very distinctive patterns in this patch of sky, but there are still a number of features that we can match up.  For instance, there is a line of three stars towards the left hand edge of the image, and a bright star to the right and slightly down from the target star in the centre.  Between the target and this bright star, there's a curved line of fainter stars.

I've highlighted these areas on the attached file and the image below, with the image and the finder side by side.  There's a red border showing the part of the finder that corresponds with your image. Once you've matched these up you'll spot lots of other matching patterns between the image and the finder.


[ Right-click and select "View image" to see full size version ]

Picture of Sarah Toney

Sarah Toney Post 9 (unread) in reply to 8

6 Jan 2021, 14:34

Hi Alan,

Thanks so much for the help. I'm not sure I'd have seen that myself. I will have a go at progressing with it now. 

Thanks again. 


Picture of Rebecca McManus

Rebecca McManus Post 10 (unread) in reply to 6

10 Jan 2021, 20:41

Hi Alan, 

Apologies for such a delay in responding. J368805J368807 and J368806 are the images I currently have, I'm still waiting for the repeat images to be taken. 

I think I might be able to see a couple of similarities between mine and Sarah's images but it could just be that I've looked at so many stars I'm now seeing patterns where they don't exist! 

Thank you so much in advance, 


Picture of Alan Cayless

Alan Cayless Post 13 (unread) in reply to 10

12 Jan 2021, 11:35 Edited by the author on 12 Jan 2021, 11:35

Hi Becky;

Thanks for the image numbers.  I've had a look at the images and I can see what's happened.

Your images have ended up being of a slightly different part of the sky, so they are indeed different from the finder chart.

The FITS header contains the coordinates.  In your images, the Right Ascension (RA) is listed as 05:02:55, but the actual coordinates for EW 2 are 05:28:55, so it's taken the image, but not in the right place.   This is far enough away that it doesn't overlap with the finder chart, and that would explain why you were finding it difficult to match up the star patterns.

This can easily happen - I've done it myself many times.  Best thing to do would be to request another set, checking the coordinates carefully when entering them.  They'll than get taken once we've got the snow and ice cleared and the weather station fixed !


Picture of Rebecca McManus

Rebecca McManus Post 14 (unread) in reply to 13

23 Jan 2021, 14:46

Hi Alan, 

Thanks so much, hopefully I'll have more success with new images! 

In terms of the actual course content relating to this activity - I think it would be really helpful to have screens shotted examples of what a result image from COAST might look like next to the finder charts with the target and reference stars labelled. That way issues such as scale and orientation of the image might be more obvious to people.

Just a thought, thanks for your continued assistance!


Picture of Alan Cayless

Alan Cayless Post 15 (unread) in reply to 14

23 Jan 2021, 16:23

Thanks Becky;

That's a good idea.  I might also try doing an updated video showing how to find and match up the stars against the finder chart.


Picture of Rebecca McManus

Rebecca McManus Post 11 (unread) in reply to 5

10 Jan 2021, 20:42

Hi Sarah, 

Thanks so much for responding! It's good to know that it's as tricky as it seemed to be and I'm not just being daft! 

Picture of Sarah Toney

Sarah Toney Post 12 (unread) in reply to 11

11 Jan 2021, 17:26

Hi Becky. No problem. I'd still be staring at my images now without Alan's help. As it is I've now finished the course. It gets easier once you've identified your stars (or Alan has :) 



Take your learning further371

Making the decision to study can be a big step, which is why you'll want a trusted University. The Open University has 50 years’ experience delivering flexible learning and 170,000 students are studying with us right now. Take a look at all Open University courses372.

If you are new to university level study, we offer two introductory routes to our qualifications. Find out Where to take your learning next?373 You could either choose to start with an Access courses374or an open box module, which allows you to count your previous learning towards an Open University qualification.

Not ready for University study then browse over 1000 free courses on OpenLearn375 and sign up to our newsletter376 to hear about new free courses as they are released.

Every year, thousands of students decide to study with The Open University. With over 120 qualifications, we’ve got the right course for you.

Request an Open University prospectus371