Imaging over the meridian

[Black Knight]

Please excuse the probably daft questions coming up .

Where I place my scope at the moment, I only have a short window of a couple of hours or so imaging time before my targets disappear below the trees in my neighbours garden. Basically from just west of south down to the treeline in the south west. What I would like to do is extend my imaging time by moving the telescope to a different location so I would be imaging both before and after the meridian.

Is it easy to "merge" images taken after a meridian flip? Presumably any images taken following the flip would need to be oriented to line up with pre-flip images, is that correct? I am currently imaging using a Canon DSLR using Raw files.

What happens when the mount reaches the meridian? Does it flip automatically, or would I need to stop imaging and reorient the scope when it reaches the meridian? I'm not using EQMod, just the normal Synscan handset.

Is there anything else I need to be aware of when doing this?

Thanks,

[martin_h]

Please excuse the probably daft questions coming up .

Is it easy to "merge" images taken after a meridian flip? Presumably any images taken following the flip would need to be oriented to line up with pre-flip images, is that correct? I am currently imaging using a Canon DSLR using Raw files.

If you use DSS for stacking you can just chuck the lot in and it sorts it all out for you.

You need to be close with alignment or you will loose a bit(or a lot) of the image round the sides when they are stacked.

I dont know if the handset does a flip or not, but EQmod will, you still have to re-align tho, depending on how accurate your alignment model is.

[Black Knight]

If you use DSS for stacking you can just chuck the lot in and it sorts it all out for you.

You need to be close with alignment or you will loose a bit(or a lot) of the image round the sides when they are stacked.

I dont know if the handset does a flip or not, but EQmod will, you still have to re-align tho, depending on how accurate your alignment model is.

Ahh, right . I didn't know DSS would do that. That puts my mind at ease. I had been sort of putting off this whole thing because I thought it might get really tricky.

When you say I will need to re-align following the meridian flip, do you mean re-frame the target etc?

[Digz]

The only difference as well between them will be 180d so they could be rotated. Seeing as DSS can handle it then happy days

After a meridian flip I think you will need to re-frame to ensure that your target is framed in roughly the same position as before otherwise you will lose data at the edges.

I was having this same dilemma a week or so ago and yet have worked out how to force my mount to flip.

[Whippy]

I dont know if the handset does a flip or not, but EQmod will, you still have to re-align tho, depending on how accurate your alignment model is.

The synscan handset does do meridian flips, all you have to do is re-select the target again and the mount does the rest.

Tony..

[Black Knight]

So I guess I'll just have to stop imaging when approaching the meridian, and then twiddle my thumbs until I can re-frame and restart after the meridian then

[Black Knight]

The synscan handset does do meridian flips, all you have to do is re-select the target again and the mount does the rest.

Tony..

Aha! OK, that's excellent! Thanks Tony, much obliged

[Digz]

Tony, thats interesting. When you say re-select the target what exactly do you have to do? If Im right the mount will keep tracking potentially causing the scope to collide - how do you stop this? DO you have to manually watch the mount and stop and chose the target again?

The above assumes no EQMOD being used.

[Whippy]

Assuming you're still on the same screen after you've selected the object all you have to do is press 'enter' twice (first time confirms you want to view the object) and off it goes. You could always just punch in the object number too, just rememebr that the mount has to be tracking the 'wrong' side of the meridian first .

Tony..

[Digz]

Cheers Tony, I thought that might be case. I guess I can just watch the object and when it about to cross the meridian I can stop imaging and perform the flip and restart again

[Whippy]

That's pretty much it really, but I'd leave it until it goes a bit past the meridian, it'll track as normal until something hits the tripod! After the flip has been done, it's just a case of re-framing (I normally turn the camera round 180 degrees to help), re-calibrating the guiding and off you go.

Tony..

[Digz]

Sweet, cheers Tony.

Sorry Andy Ill stop hijacking your thread now

[chrisshillito]

Cheers Tony, I thought that might be case. I guess I can just watch the object and when it about to cross the meridian I can stop imaging and perform the flip and restart again

Yes perform the flip, reframe, recalibrate your autoguider, refocus (you can bet something shifted during the flip) etc. etc.

Much easier to just to track through the meridian if you can. Most equipment can go a few hours past without collision - you can always do dry run to see how long you've got.

Chris.

[Black Knight]

Sweet, cheers Tony.

Sorry Andy Ill stop hijacking your thread now

No probs Digz, I've learnt something else now

[Jannis]

*sends you a chainsaw in the post - you know what to do...*

hehe, maybe not. But, with DSS, like mentiond, it will automatically rotate the pics and stack them for you (as long as they're roughly the same at least). As the target is so far away, the angle isn't going to be changed, so you basically won't notice any difference. might be a difference if the light pollution changes though, i haven't tried that yet.

I noticed on my HEQ5 pro that it did flip around automatically if nessesery when tracking, but it doesn't always hit the target 100% like it was though, so a reframing was needed in my case at least.

On the other hand, it couldn't really decide wich way to flip, so at a point there it flipped 2 times back and forth before it was tracking normally again, no idea why this happend...

[dmahon]

Doesn't rotating the camera mean two sets of flats are needed?

[themos]

Perhaps it's better to start on the "wrong" side of the meridian, weights up, and let it carry on from there. At least that way you know that collision issues are not going to get worse.

[ollypenrice]

Perhaps it's better to start on the "wrong" side of the meridian, weights up, and let it carry on from there. At least that way you know that collision issues are not going to get worse.

But most mounts, using GoTo, won't let you. You can put them there by hand if you can see the target in the finder but time is precious. It is a pest.

I just go way past the Meridian (a pier greatly extends the time you have) then reframe using the camera. Pick some key stars around the edge of the field to use as markers.

If you have Maxim you can plate solve a new pic onto their planetarium.

If reframing alignment is very critical on a particular shot I take a test pic and use Registar to drop it onto a copy of the original. This is pretty quick. It is confusing that the original is the other way up so I put an inverted copy on the screen to look at when reframing. Artemis Capture gives me the option of inverting the post-flip image but I don't use it because I get in a muddle with darks if I do.

But the flip is a pain in the derriere and I detest having to do them. Oh for one of those whacking great one-armed mounts that cares not a whit either for balance of for the meridian...

Olly

[themos]

I find that I have to plate solve more often than not. It's not a big hassle, I just take a low-res JPEG of 30 sec exposure and upload it to live.astrometry.net. That gives me an RA/DEC for the centre of field so I use EQTour to sync with those coordinates and then do a GoTo the target (if it would execute without a flip). If I am already on the wrong side of the meridian, I would just use EQTour to tell me the RA/DEC coordinates of the target and then slew the mount to those coordinates (not GoTo).

[ollypenrice]

I find that I have to plate solve more often than not. It's not a big hassle, I just take a low-res JPEG of 30 sec exposure and upload it to live.astrometry.net. That gives me an RA/DEC for the centre of field so I use EQTour to sync with those coordinates and then do a GoTo the target (if it would execute without a flip). If I am already on the wrong side of the meridian, I would just use EQTour to tell me the RA/DEC coordinates of the target and then slew the mount to those coordinates (not GoTo).

This sounds very cute indeed but can you point us to the right site? I can't find it any plate solving facility on the one I found.

Olly

[Psychobilly]

You could apply to sign up as a beta tester in the past .. or you can use the flickr group

Flickr: astrometry

Peter....

[martin_h]

I always image across the meridian and flip when required, I use a rotated 180deg image to align to using al's reticule on a bright star or galaxy centre etc, I know I'm not going to be 100% accurate but I find its close enough and only loose a bit around the edges when stacking. I put my camera on 1 second 4x binned loops to adjust the image in the frame

[themos]

Yes, the flickr interface to astrometry,.net will give you what you need but I don't know what turnaround time you can expect. For a non-network solution , you can try Elbrus although it takes a bit of hacking.

[daz]

Doesn't rotating the camera mean two sets of flats are needed?

Yep! You would need to do a set before and after flipping in this case.

I don't move the camera, and just flip the images in Maxim when I have calibrated them