FaB-Bo-Peep

Testing of my new Sky-Watcher ED72 continues. The nights are ridiculously short in terms of darkness but as clear skies are a rarity these days, I have to seize each opportunity. This is a total of 45 minutes, (15 x 3 mins), of data of NGC6888 - The Crescent Nebula. Taken from my light polluted back garden and not a target I have ever looked at before. As always it amazes me just how much I can capture from my small back garden, oh the vastness of space! While it does not have the magnification of my bigger scope, the ED72 is just so quick and easy to setup and dismantle, I think it's going to make me very lazy. Camera is a Canon Rebel XS, (1000D) and filter was an Optolong L-Pro, all controlled through my ASI Air Pro.

I think the Canon DSLR + "T"-ring pretty much gives the suggested 55mm and that was where my initial image was taken. 

Last night I added a 9mm spacer which obviously takes me way passed the recommended but I think the results speak for themselves but also think I still need to add a little more. 

The below snip is a side by side comparison of the bottom left part of a single sub from my original image vs the same area of last nights with the 9mm spacer ring.

Ok so I bought a set of T2 / M42 extension tubes of 4/5/6/7/8/9mm to go between my camera and the OVL field flattener. Last night I had a play with the 9mm, figuring that should show a difference even if it ended up being too much. Anyway in my opinion this has significantly improved things but to me it still looks like a little more is needed so I will keep increasing by using combinations of the spacers until I feel like it's peaked.  I also used a Bahtinov focus mask which clearly showed that focus on my previous attempt was a fair way off.  Attached is a processed image with only the very edges of the frame cropped to remove stacking artefacts and nothing applied to the star shapes.  Do you also think it's moving in the right direction?

I'm in the process of gathering together a lightweight and easily transportable wide field system so I can venture further afield than my back garden. This is going to be based around a Skywatcher 72ED and an AZ-GTI, (in EQ mode). I'm still lacking a tripod and polar wedge to finish the mount but took the last clear night as an opportunity to try the scope on my EQ6 GT.

I stacked all 15 of the 3 minute subs gathered in DSS and then processed them in Startools and Gimp.

Additional equipment used: OVL field flattener, Canon Rebel XS, (1000D), Optolong L-Pro filter, Skywatcher finder scope used as guidescope with ASI-120MC-S and of course my ASI AIR Pro.

Did you get this sorted? I've just taken delivery of a Skywatcher 72ED and OVL field flattener and have elongated stars around the edge of the image radiating out from the centre so believe I need some additional spacing between the field flattener and the camera?

Thanks Michael, I've ordered some spacers to see if they improve things. Even if I jump from too close to too far, at least this will hopefully tell me that "just right" is somewhere in between.

This image has confused me even further, where exactly am I supposed to add extra spacing? I thought it was between the flattener and the camera, not the flattener and the telescope?

On 13/09/2018 at 13:41, billyharris72 said:

Hi all:

I've just had a first go with my new scope (Skywatcher ED72 with OVL flattener) and early signs are good - think it's going to be a keeper. However, I'm struggling with what I assume is field curvature (never imaged with a frac before so this is new for me). The stars in and around the centre are great but at the edges of the field they are both out of focus and elongated (pointing towards and away from the centre of the image). I just had a couple of questions that I was hoping someone more experienced could weigh in on:

1) Does that sound like field curvature? (90% sure it is but worth asking)?

2) The effect is not equal in all corners (some are actually not too bad). Now I think the setup is square - could this be a distance issue, or do I need to work more on getting the setup square (and if so, any ideas on how / what helps)?

3) On the off chance someone has already dealt with this, does anyone out there know the correct sensor distance for this scope and flattener combo? Initial messing about suggests I might need more than 55mm, but any pointers would be really useful.

4) If not, is it possible to infer anything about the spacing (whether I need more or less) from looking at the curvature?

Sorry ... that's not a couple of questions after all.

Cheers,

Billy

Did you ever resolve this Billy? I've just taken delivery of an ED72 and OVL field flattener and am experiencing exactly the same issue

Hi everyone,

I've just taken delivery of the above and was anticipating a nice flat field with round stars all the way to the edges of images but frustratingly things are never that easy.

Some corners are worse than others but to various degrees, the stars all appear to point towards / away from the centre of the image which leads me to believe the DSLR camera sensor is too close but too close to what, the OVL field flattener? If this is indeed the issue, what spacers are needed please and how / where do I put them?

Thanks in advance

🙂

Thanks Victor, I would be very happy with an image like that, (especially your version with the false luminance layer). 

Hi everyone,

I'm trying to put together a compact and lightweight travel setup for taking on holiday and venturing further afield than my back garden.

I think I've narrowed it down to:

*Skywatcher 72ED DS Pro.

*OVL field flattener.

*Sky-Watcher Star Adventurer 2i Wi-Fi Pro Pack. I would also purchase a shutter release cable to allow the Star Adventurer to control the camera via the app.

These would be used with my existing Canon Rebel XS (1000D), for which I already have a T ring.

Are these a good match? I've seen several disturbing reports of people struggling to obtain a flat field with the 72ED + flattener and having to use spacers which in turn leads to an issue of lack of inward focus?

Any better options for a similar budget?

If anyone has example photos taken with the 72ED + OVL flattener I would love to see them please.

Thanks in advance

😀

M63, (the Sunflower Galaxy). This image is the result of 72 minutes worth of data and I pushed my camera to 4 minute individual exposures, (my L-Pro light pollution filter again proved a worthwhile purchase). As I was capturing the data I was not at all confident about how the final image would turn out as the galaxy was positioned in the same area of sky as the moon which added to my usual light pollution woes. But it's safe to say this is my best image of this object so far and it makes me wonder what it would have been like if the moon was not out. I guess I will have to revisit it again at some point to find out. Camera was a Rebel XS, (1000D), Scope was a Skywatcher 250PDS, Mount was an AZ-EQ6 GT.

Absolutely stunning! What coma corrector do you use please as apart from the amazing image, I am also very envious of your lovely round stars. 🙂

So after sorting out my out of focus guide scope I then had an amazingly quick polar alignment thanks to my ASI AIR Pro. Then I encountered challenge number 2 in that everything I set up to image transited behind various telephone wires running to houses in our area causing all sorts of funny colours as the various street lights reflected off them, (see 2nd photo). Anyway I did manage to obtain this image of M97, the Owl nebula. I captured some data before it went behind a telephone wire and then returned to it later in the night to capture some more once it had cleared the wire. Total data acquisition was about 1 hour which is way more than I have spent imaging any single target lately and combining data from 2 separate times is not something I have ever done before and was largely made possible by the fact that my ASI AIR Pro centres each target allowing 2 sets of data to be easily aligned. I was also using the L-Pro light pollution filter which I purchased last year and have only just started using and that's amazing! This image is largely made up of 3 minute exposures which prior to the filter would have been impossible as the light pollution would have turned everything into a bright, (washed out), mess. The stars in the bottom left are a bit out of shape and I believe the focuser on my imaging scope might not be flat to the imaging path, (possibly due to the weight of the camera), so I will have to look into adjusting this. I have tried imaging the Owl Nebula before but had no previous results worthy of posting, but this on the other hand is way better than my previous attempts and therefore worth sharing. Imaging scope is a Skywatcher 250PDS mounted on an AZ-EQ6 GT. Imaging camera is a Canon rebel XS, (1000D).

Thanks for all the advice, all very helpful for further development but sorting out the DSS settings has got me back to where I thought I should be.

Here's a couple of very rough + ready DSS stacks onward processed with my very limited knowledge in Startools. While I fully appreciate they will not win any awards, I can at least say they are now better than my previous attempts which with the addition of the LPRO filter is exactly where I thought I should be 🙂

p.s. please don't bother trying to process the stack in my original post, as jager945 points out, it has multiple issues largely due to incorrect stacking settings in DSS.

Thank you so much jager945, I appreciate I've still got a long way to go on this journey but having implemented the DSS settings you linked to my results are far improved and already look better than last years attempts 🙂

Thanks for the above reply, while I am always looking to progress, I am none the less confused as to why I cannot at least equal what I have previously achieved.

Taking the points you mention:

• I will certainly look at this.
• Interesting, I am certainly drizzling for the first time this year, (using an ASIAIR PRO), and thought it only had positive impact but maybe not.  ****Correction, I am "dithering" with the ASIAIR PRO, not even sure what drizzling is so need to check how this is happening****
• I fully understand that flats would have a positive effect but to date I have not ventured into using them so as I have never used them I would expect my results from this year to be similar to previous years.
• I have not changed anything on the camera so is the "colour balancing" something that is occurring in DSS? I have re-installed a new version on a new computer so maybe it's an option I have inadvertently enabled?

Hi everyone,

The attached is about 30 minutes of RAW files taken with a Skywatcher 250PDS, AZ-EQ6, Canon Rebel XS, (1000D), and Optolong L-PRO filter, stacked in DSS.

This is very similar to my total integration time per target from previous years but no mater what target I attempt I'm simply just not getting results comparable to last year and the only thing I've added in the optical train is the Optolong LPRO which I can't think for one minute is my issue but next session I will try without it just as a test.

Anyway, just in case I am messing up with the latest version of Startools, I would be very grateful if some of you could please have a quick play with the attached and post your end result.

Thanks in advance

🙂

M81-DSS-FITS.FTS

I've deliberated over this for ages but think it might be time to let this go to a new home as I'm simply not using it and it's just sitting in it's box gathering dust which seems such a waste. 

It's been stored for many years and could benefit from a good clean, (which I will not attempt for fear of causing more harm than good). 

There is a small mark on the rear mirror which I've tried to show in the last photo but this does not impact its performance and of course the usual cosmetic wear and tear.

The box states G-8 optical tube assembly but this is a C8 yes?

A Celestron f/6.3 focal reducer is also included.

I know it's worth whatever someone will pay for it but what do you feel would be a good starting price please?

Thanks in advance

🙂

I knew it, immediately after posting this question I found a little power button symbol in the app which when  click says "Shut down ASI AIR PRO and APP", it's located in the wifi settings....... of course!

Hi everyone, I feel very silly for having to ask this as I'm sure the answer must be staring me in the face but here goes.  I just received my ASI AIR Pro and immediately backed up the original micro SD card and restored it to a blank and am now up + running with the newly created card with the original safely stored away. One silly question though, how do you safely shut the ASI AIR PRO down? Do you simply turn off the switch? That appears a sure way of corrupting something. I saw something on the web about shutting the app down and leaving it for 15 seconds before switching the AIR off but I also cannot find any obvious way of exiting the Android app, surely you don't have to "force stop" it?

Thanks in advance.

:-)

A couple of shots of Jupiter along with 3 of it's moons from last night, (processed in slightly different ways). I managed to grab these before it disappeared behind the tree this time and it's safe to say they are my best so far. The raging storm that creates Jupiter’s great red spot has waned and turned the planet’s famous blemish to orange and although this is not always visible as the planet rotates, if you look closely at the outer edge, (at around the 11 o'clock position), you can just about see it before it disappears behind the planet.

They are the results of some very short AVI files, captured in ASI Capture and stacked in AS!S, (because registax6 would not load the files).

Scope is a Skywatcher 250PDS and camera is a ZWO ASI 120MC.

🙂

Absolutely stunning!

I recently had the same dilemma and ended up going for the Optolong L-Pro. I'm still waiting for it to be delivered so have not actually tested it myself but all the reviews I've seen have been very favourable. Looking at the transmission graphs it's less aggressive with the amount of light it blocks, (there are 3 additional light passing wavelength peaks on the L-Pro graph compared to the CLS), and it's my understanding that while it's not quite as good at blocking light pollution, the results are much more naturally balanced straight from the camera with stars retaining much more of their natural colour which obviously makes things so much easier in post processing. It's my understanding that the aggressive CLS filter blocks some good light along with light pollution and therefore some colours are just absent from images and while post processing / using a customs white balance can help to some degree, at the end of the day the missing colours can not be brought back as they are just gone.

A CLS filter is a good budget choice and can be an absolute blessing in heavily light polluted areas where it can make the difference between having an image or not having one! For an un-modified DSLR just go for the normal version, (i.e. not the CCD variant which is for modified cameras which have had their internal IR cut filter removed).

The L-Pro is a much more complex filter allowing through more of the good light but is consequently harder to manufacture and therefore more expensive but seeing the results that some forum members are achieving with it and knowing my limited processing skills, if it means I achieve a more natural colour balance straight out of the camera then I consider it money well spent, (and I do love my coloured stars).

Needless to say I will of course post my actual findings once I've received it and given it a go.

Hope this helps a little

🙂