With a clear weekend in the forecast and some cottage time coming up I finally got a chance for some imaging time. Skies at the cottage in Marion Bridge are reasonably dark with the Milky Way clearly visible. I’ve been itching to get out for the final testing of my Esprit 120. After SkyWatcher shipped me a replacement Esprit to replace a unit with pinched optics, I noticed a strange distortion in some of the stars in several of my images. The distortion only showed up after saturation boosts so I wanted to do some more testing to figure out what was causing the problem. After shooting several star fields at varying altitudes I very pleased with the results. It turns out that the distorted stars were due to atmospheric dispersion and saturation boosting during processing. Aligning the three colour channels before any other processing completely solves the problem and the scope produces stunning images as advertised.
First up is a shot of M13. I was imaging the cluster as one of my test shots to verify the atmospheric dispersion problem. The shot was taken from our cottage and the cluster was almost directly overhead.
The image is a 50 minute exposure with round stars right to the corners. Several field galaxies are visible in the full res version of the shot with NGC 6207 in the upper right of the image.
Since the night was supposed to be clear until morning the next target up was M57. This was a chance to check how much true resolution I was going to loose by moving from an eight inch reflector to a 4.7 inch refractor as I have an image of this target taken with my reflector.
The shot is a 69 minute exposure made from a stack of 23, three minute subs. The 15’th magnitude galaxy PGC62532 is easily visible to the upper left of M57 and there are galaxies down to 17’th magnitude in the field.
Over several nights I managed to capture over five hours on Ngc7497. This is an unimpressive nearby galaxy about 60 million light years distant. The interesting part about imaging this galaxy is the gas and dust that fills the field. The dust is much closer than the galaxy being inside the Milky Way. The shot could use over ten hours to really bring out the detail in the very faint dust field, but all in all it turned out quite well given that is was shot with a DSLR.
Once vacation ended it was back to the work day grind, but with another clear weekend I couldn’t resist a little more imaging time. This time several members of the local RASC Centre headed out to the St. Croix Observatory (SCO), the Centre’s roll off observatory in some dark skies about 40 minutes outside the city. Since I had to get into work at a reasonable time the next morning I had to image something bright in the limited time I had so I decided to give M8 a try. The seeing was not the best with PHD showing around two arcseconds guide errors so I wasn’t sure how the stars in the field would turn out, but the software did a great job and the stars were very tight and circular all the way to the corners of the image.
With the weather here in Nova Scotia this has been a productive summer of imaging and the Esprit 120 seems to be a great imaging platform, performing as advertised.
After reshooting some flats to get rid of a gradient in the lower part of the image I was able to push the stretch a bit more and managed to get a more detailed image of the main galaxy (M51) in my last post. The image below is a crop of the central portion of the Esprit 120 image from my last post after applying the new flats.
It’s been a few months since I’ve had clear skies during a dark sky imaging window. I’ve been itching to get out and get a good test of my new SkyWatcher Esprit 120 APO. Several members of the Halifax Centre of the RASC arrived at the St. Croix Observatory (SCO) and we all sat around until just past 11PM when the clouds parted revealing some of the most transparent sky I seen at the site. The Milky Way was visible right to the horizon.
After setting up and polar aligning I swung the scope around to M51 and started imaging. When the first image came off the camera I was very pleased to see that I didn’t give up much in terms of resolution compared to my eight inch Newtonian. The refractor produces a nice crisp image with a slightly wider field.
As an added surprise there is some of the IFN visible throughout the field, but I have to redo my flats to really bring it out as my current flat is causing a lighter strip across the bottom of the image.
Here is a version off the Newtonian for comparison. The image is a shorter exposure so it is not stretched as much, but as you can see the core resolution is no better then the Esprit.
Well it has been a while coming, but the folks at SkyWatcher were able to diagnose the problem they had with my previous Esprit 120 and have shipped me a new replacement scope. I’m very pleased to say that this new unit performs as expected and as advertised, at least in my limited testing. I was able to get out for an hour last night and take a few test shots to verify that the optical problem is no more. The star images are what you would expect from a higher end refractor, no spikes, round and small halos. Below is a quick 12 minute (6 by 2 minute subs) shot of M51 taken with the scope.
Please excuse the poor image quality, it is a result of a very short exposure from an urban imaging site with the Moon in the sky. Even with that limitation there are 15’th magnitude smudges in the upper right that are some of the faint galaxies around the Whirlpool. Of more interest to me is the quality of the star images. Here is a zoom in on the double in the upper left corner.
As you can see the stars are nice and round with no trace of the nasty spikes that showed up on the previous units and these are stars at the corner of the frame, not in the center.
I’d like to say thanks to Joe Wang at Pacific Telescope Sales & Marketing and the folks at Atlantic Photo Supply (local SkyWatcher dealer) for going the extra mile in customer service to satisfy a grumpy customer after my initial purchase had less than stellar performance.
Now if the weather will just cooperate a bit, I can’t wait to see what the Esprit 120 can do under much darker skies.
Well I’ve had a chance to take the Esprit 120 on a good test drive and it has been a bit of a disappointment. The new scope sent from SkyWatcher Canada still has strange spikes on the stars and SkyWatcher Canada tells me that all of their stock seems to have the same problem. Take a look at the star image below.
Not the nicest stellar image; especially since I bought the refractor, in part, to get rid of diffraction spikes from my reflector. It seems there is a problem with at least one batch of the scopes. SkyWatcher has been very good and forthcoming about the issue and is looking into the problem to get me a scope that works as advertised. I know the scope can perform well from several great reviews so stay tuned as I wait for the factory to look into the problem.
Recently I purchased a shiny new SkyWatcher Esprit 120 APO refractor from Atlantic Photo Supply. Unlike what you see in the usual astronomy magazines my new toy had some issues with spikes on all the stars that were not what I expected of a premium refractor. I contacted the good folks at Atlantic Photo supply to let them know and They immediately contacted SkyWatcher and forwarded my initial test images.
Now this blog entry is not about complaining that the scope had issues. Instead it is about the great customer service offered to me by both Atlantic Photo Supply and the folks at SkyWatcher. No one gave me any grief about my test methods or questioned my conclusions, in fact SkyWatcher immediately picked out another scope, tested it and sent it to me with instructions to simply swap out the optical tube and ship it back to them at their expense. With the Christmas holidays fast approaching they got the scope shipped off to Atlantic Photo Supply and it arrived a week later. All that was required of me was to drop the problematic scope off and pick up the new, tested unit.
After hooking everything up I hauled it all out to my driveway for testing. Now my driveway is in an urban location with a bright sky measured at 18 to 19 mag/arcsecond squared on a good night. Initial views through the scope with a 22 mm Nagler eyepiece were spectacular delivering pinpoint stars across the two degree field. Popping in a 5 mm eyepiece showed classic diffraction patterns that were identical both sides of focus with no trace of any colour issues.
Now the views were great, but I didn’t buy the scope to look through; it will be a photographic workhorse replacing my eight inch f/5 Newtonian. Replacing the eyepiece holder with the supplied field flattener and mounting my Canon 60Da I spent a few minutes shooting Deneb to see if the strange spikes were still there and I’m glad to report that the star images were pinpoints edge to edge offering the performance expected of a premium refractor. Next I tried a quick five and a half minute exposure of M42 with the resulting image shown below.
The scope produced a very nice image with pinpoint stars across the field with lots of detail in the core of the nebula. The image above did not use any calibration frames. My 60Da has built in dark suppression so no dark frames were required and the flat field of the Esprit 120 means I did not need any flat frames.
Looking at the stars in a corner of the image you can see that they remain sharp and show no colour fringing.
All in all the scope makes an excellent imaging platform and the customer service from SkyWatcher and Atlantic Photo Supply was second to none, quickly responding to problems with the initial delivered product to get me up and running even over the holidays.
The day started out normally, warm sunny and promising to be another great summer day. The weather forecast called for a mix of sun and cloud with a chance of showers and clearing in the evening. After doing the inevitable cottage chores I started putting the scope together in our shed. Since the drive to the cottage involves some less than smooth dirt roads, I went about aligning the optics and getting all the equipment together.
When supper time rolled around, our family wandered up to our neighbours to join in an 80’th birthday celebration for a long time friend. After shooting pictures at the event I dashed home to let our dog out for a bathroom break and looked up at the sky. Things were getting very dark and it was only 6 PM! It seems our chance of showers had turned into a severe thunder storm warning and a tornado warning! After taking the dog out I was planning to rejoin the birthday party, but the heavens opened up with heavy rain so I ran to the shed and closed the door to protect the scope and then dashed inside the cottage just as the wind started picking up. By the time I got dried off it was raining heavily as you can see from the picture below.After drying off I took a look out the window, just before taking the picture to see a small water spout rip our row boat off the wharf and send it 40 feet down river before landing with a splash! Ten minutes later it was all over and the Sun started to break through the clouds.
By 9:00PM the skies began to clear and the wind died down to zero allowing our kids to enjoy a fire by the rivers edge while I got a chance to do some night scape work.
By about 10:30 it was one of the clearest nights I had at the cottage. I hauled the scope and camera out of the shed and set up to try to capture some data from M20. This has always been a tricky target from the cottage as it skirts the trees for most of time. I managed to image it for about two hours only getting 72 minutes of data where the trees did not interfere. After a little processing it turned out reasonably well.
For details on the image acquisition and processing see my imaging site.
Sometimes things go right despite my best efforts. Friday night was such a night. My local centre of the RASC decided to have a club observer’s evening and like a lot of members I couldn’t resist the first clear night of spring so I packed my car with my gear in the morning and headed to SCO(St.. Croix Observatory) after work for an evening under the stars. When I arrived there was already a small crowd of 21 setting up. I to started out simple enough, I started early so I would have plenty of daylight while setting up my scope then things started to go wrong. With the first stars appearing I aligned on m wrong star and spent 30 minutes wondering why none of the alignment stars were near the center of the field. After discovering my error I realigned correctly and got down to the business of focusing. With a mask and live view focusing is generally an easy task, but with my first target being the galactic jet in M86 I needed a barlow and I soon realized that I didn’t have my 2 inch extension tube and couldn’t get focus. After borrowing one from a friend I managed to get the camera to come to proper focus and the imaging began.
First up was the galactic jet in M86. I had imaged this one before with some success, but my optics at the time left a little to be desired. My first attempt was several years ago with Meade optics (f/4 Schmidt Newtonian) that suffered from a bit of astigmatism and my processing tool kit was a little sparse, but I still managed to get some evidence of the jet.
It was a 300 second exposure that was the sum of ten, 30 second exposures that just barely proved sufficient to show the jet.
This latest attempt was the average of 15, two minute exposures with a longer focal length. The result was pretty noisy and it took a bit of processing in Images Plus. There was a lot of horizontal and vertical banding pattern noise that was easy to clean up using this method as a guide.
The jet is clearly visible at the top of the galaxy and even has a pale blue colour.
Next up was M86 and the heart of Markarian’s Chain. For this one I removed the barlow and imaged at prime focus. M86 is an elliptical galaxy moving toward the heart of the Virgo Cluster and forms the nose in the galactic smiley face below.
The shot is the average of 23, four minute subs for a total of 92 minutes. Processed on Images Plus with my usual masked stretched, split star technique to keep the stars small and bring the galaxies out from the background. When examining the full scale image there are over 30 galaxies in the field.
With my imaging done for the night I packed up and headed home and was treated to a spectacular Moon rise in the approaching cloud. Unfortunately with my camera packed in the trunk with my gear and being on a busy highway late at night I couldn’t stop to image it.
Ever have one of those nights when things just don’t seem to start well? Turns out that this was one of those nights. A friend and I went to our club’s dark sky site to capture a couple of images, I was trying for Thor’s Helmet while my friend was imaging the Cone Nebula. It was nice to set up our scopes without needing gloves, but soon the temperature started to drop and that’s when things started to go wrong.
First thing that failed was the switches used to find the home position on the mount. Some moisture froze and the RA switch stuck forcing manual home positioning. Next up I had an issue with the RA guiding. Seems that I didn’t do a great job in balancing the RA axis and my guiding produced odd double stars. The solution was simple, rebalance and adjust some of the PHD settings, but it cost me 30 minutes of adjustment and realignment. Since it was a work day in the morning this meant a shorter than intended exposure for the evening. After focusing again and starting the exposure I noticed the battery was failing in my trusty intervolometer. Fortunately it lasted through the session and the imaging finally got underway.
The Saint Croix Observatory is a wonderful facility owned and operated by the Halifax Centre of the RASC. The facility has a much appreciated warm room that we made good use of for the rest of the evening while the cameras and scopes did all the work to collect data for our images. By the time we packed up I had collected 112 minutes of data on Thor’s Helmet, an emission nebula surrounding a Wolf-Rayet star. The image was calibrated with flats, flat darks and bias frames. Darks were not used as my 60Da has built in dark suppression that does a great job of removing the dark current from the system. I simply shot three one minute darks to average and use as a hot pixel map and processed the data in Images Plus. After a little post processing the image turned out reasonably well for the shorter than intended exposure.
After a bit of a dry spell a couple of RASC members and I made it out to the St. Croix Observatory (SCO). SCO is the local Centre club observatory with dark skies and a great roll off facility. One thing that we really appreciated was the warm room as it was -10 degrees C during the imaging run!
After setting up and polar aligning, the wind picked up and caused a lot of guiding problems. The result was fat, but round stars and a blurred nebula. The image below is a simple stretch of the calibrated and stacked data.
The image is definitely not one of my best but with a little work I was able to rescue it, well sort of…All the processing was done with Images Plus employing split star techniques, masked stretching and star reduction. The masked stretches help to control the star bloat that would otherwise ruin the image. for those that want some details on the type of processing involved, check out this paper on the technique.
The image is the average of 40 three minute subs calibrated with bias, flats and flat darks. No dark frames were used as my Canon 60Da has built in dark suppression so they are not necessary. A single dark was used as a hot pixel map using the adaptive high/low pixel reduction functions of Images Plus. When I first started using this technique I was skeptical, but after making some measurements the technique really does work and it save quite a bit of time when you don’t have to shoot darks at the end of an imaging run.
Clear skies and keep imaging.