gregbradley
06-01-2009, 01:22 PM
Here is a link to one of my setups:
http://www.pbase.com/image/107845851
I used this extensively over the last 9 days.
It is a Tak BRC 250 (Ritchie Chretien with Baker flattener/corrector at F5)
on a Tak NJP mount and FLI PDF digital focuser, FLI CFW 4/5 50mm square filter wheel and FLI ML8300 camera.
Tak BRC 250:
This is extremely well built and well finished off. It is typical Tak high quality and strongly built. It is F5 which is unheard of in the RC world. usually they are F9 with a fast one being around F7 although there are rare ones at F6.2.
This scope is 10 inches of aperture so it gets a lot of resolution. The helical focuser is designed to move the corrector lens out with the focus. But the focuser is difficult to use as it requires loosening off the overall rotator (the first captains wheel), spinning the whole unit whilst holding the corrector so the camera does not turn with it.
I have attached a FLI PDF focuser to the imaging train and this is a marvellous unit that makes exact focus a breeze.
It is a little bit heavy but handleable. It is fairly compact for a 10 inch RC which is a plus and makes it a bit easier to transport.
The BRC is also wind resistant and I was able to image in heavy winds at my observatory so that is a big plus for me as my dark site can be windy at times(the walls are about 2.2 metres high but an RCOS 12.5 inch would stick above the walls into the wind stream and not be useable if winds were higher than about 10kmh).
The spider is quite thick so the diffraction spikes are a bit thickish in images and it does tend to square off some brighter stars a bit but really I don't find that objectionable and the advantages outweigh that.
The corrector has a temperature compensating cell which has 4 rods that match the expansion coefficient of the tube fairly closely. Whilst focus is not exactly the same over 5C difference it is extremely close.
F5 is awesome and bright images are obtained quite quickly. No scope is best for all users but it suits my particular needs very well given I travel 3.5 hours to my dark site and sometimes it is windy and I usually cannot spend 15 hours on one object. 5-6 hours on any object seems to get enough signal to noise ratio to do the job at the expense of a smaller image scale on galaxies but still frames them up nicely.
I give the Tak BRC 250 9 out of 10 with the 1 point deduction for the awkward native focusing arrangement.
FLI PDF Focuser: A thin unit (about 27mm or so) and easy to install. It is fuss free and you simply click on the controlling software to move it. I use CCDsoft and it is so convenient to have a number connected with a focus position. Checking and getting exact focus only takes about 3 minutes or less. I give this focuser 9 out of 10 with 1 point deduction for not providing software to run it independently so it will do autofocusing.
Tak NJP mount:
Tak no longer makes the NJP mount having moved on to the EM400. The NJP mount is a marvellous piece of equipment. It is quite manhandleable weightwise.
The first thing I liked about it is its simplicity. I can turn this beauty on, line it up with a bright star and sync it once and it will be quite closely aligned. No need for 10 or more syncs with Gemini system. It does not have a provision for PEC but its PE is extremely low. I graphed one run a while ago and was surprised to see 1.95 arc seconds peak to peak which is extremely low.
It does not have lots of electronic bells and whistles and I like this having my hands full with cameras and filter wheels etc. Some will prefer more electronic control, I like the ease and user friendliness of it.
It has a few quirks. For southern users you have to hold down one of the hand controller buttons when turing it on to set it for southern hemisphere. A bit like those watches you buy with the complicated instructions to get it to do something.
It has a high speed switch for slewing and a normal speed for guiding. You have to manually switch over and if you forget and start your autoguiding then the corrections will be massive and you will lose your framing and have to frame the image again. Easy to do at 3am in the morning!
It has a very high quality polar alignment scope. I don't use this as I could not get used to spotting Sigma Octans as it is too dim and hard to distinguish. Some have mastered this and report the polar scope as one of the best out there. I use drift aligning and started using the camera for the drift aligning using Startarg cross hair overlays on the screen to make the process easier.
Some also may not like the threaded counterweight rod but a smooth one is available as an accessory from Robin Cassady. I don't mind as the weights never move which I like.
The clutches are well placed and easy to use.
The mount motors make a pleasing jet like high whine as they wind up to 19,000 to do their job. They are hand wound motors.
FLI filter wheel:
This unit is good but looks a bit shabby against the superior Apogee FW50 filter wheel which is probably the best on the market. It is thin and light but is a bit slow to select a filter. It does achieve good repeatability though.
The washers for holding down the filters are a bit small and there is no provision to handle different thickness filters (it assumes 3mm thick filters - Astronomik filters are 1mm). I give this filter wheel 7 out of 10.
FLI ML8300 camera;
I love this camera. It is an awesome imaging machine. Light, small, no noise, incredible cooling, fast downloads.
It slams the temperature down to -35C when ambient is 22C in about 3 minutes or less - fantastic. It also holds the temperature without overshooting very very accurately more accurate than any other camera (the chip is small though).
No negatives about this camera except that the small well depth (25,000 electrons) means that bright stars bloat more quickly than say an STL11 or an Apogee U16M. But the chip is so defect free and noise free at -35C and very evenly illuminated with no microlense artifacts that you forgive that.
I do notice that stars show the pixels more with this camera but that is probably to do with the sampling and the higher magnification its smaller chip gives. I give this camera 9.5 out of 10 with the .5 deduction for the small well depth of the KAI8300 chip.
Greg.
http://www.pbase.com/image/107845851
I used this extensively over the last 9 days.
It is a Tak BRC 250 (Ritchie Chretien with Baker flattener/corrector at F5)
on a Tak NJP mount and FLI PDF digital focuser, FLI CFW 4/5 50mm square filter wheel and FLI ML8300 camera.
Tak BRC 250:
This is extremely well built and well finished off. It is typical Tak high quality and strongly built. It is F5 which is unheard of in the RC world. usually they are F9 with a fast one being around F7 although there are rare ones at F6.2.
This scope is 10 inches of aperture so it gets a lot of resolution. The helical focuser is designed to move the corrector lens out with the focus. But the focuser is difficult to use as it requires loosening off the overall rotator (the first captains wheel), spinning the whole unit whilst holding the corrector so the camera does not turn with it.
I have attached a FLI PDF focuser to the imaging train and this is a marvellous unit that makes exact focus a breeze.
It is a little bit heavy but handleable. It is fairly compact for a 10 inch RC which is a plus and makes it a bit easier to transport.
The BRC is also wind resistant and I was able to image in heavy winds at my observatory so that is a big plus for me as my dark site can be windy at times(the walls are about 2.2 metres high but an RCOS 12.5 inch would stick above the walls into the wind stream and not be useable if winds were higher than about 10kmh).
The spider is quite thick so the diffraction spikes are a bit thickish in images and it does tend to square off some brighter stars a bit but really I don't find that objectionable and the advantages outweigh that.
The corrector has a temperature compensating cell which has 4 rods that match the expansion coefficient of the tube fairly closely. Whilst focus is not exactly the same over 5C difference it is extremely close.
F5 is awesome and bright images are obtained quite quickly. No scope is best for all users but it suits my particular needs very well given I travel 3.5 hours to my dark site and sometimes it is windy and I usually cannot spend 15 hours on one object. 5-6 hours on any object seems to get enough signal to noise ratio to do the job at the expense of a smaller image scale on galaxies but still frames them up nicely.
I give the Tak BRC 250 9 out of 10 with the 1 point deduction for the awkward native focusing arrangement.
FLI PDF Focuser: A thin unit (about 27mm or so) and easy to install. It is fuss free and you simply click on the controlling software to move it. I use CCDsoft and it is so convenient to have a number connected with a focus position. Checking and getting exact focus only takes about 3 minutes or less. I give this focuser 9 out of 10 with 1 point deduction for not providing software to run it independently so it will do autofocusing.
Tak NJP mount:
Tak no longer makes the NJP mount having moved on to the EM400. The NJP mount is a marvellous piece of equipment. It is quite manhandleable weightwise.
The first thing I liked about it is its simplicity. I can turn this beauty on, line it up with a bright star and sync it once and it will be quite closely aligned. No need for 10 or more syncs with Gemini system. It does not have a provision for PEC but its PE is extremely low. I graphed one run a while ago and was surprised to see 1.95 arc seconds peak to peak which is extremely low.
It does not have lots of electronic bells and whistles and I like this having my hands full with cameras and filter wheels etc. Some will prefer more electronic control, I like the ease and user friendliness of it.
It has a few quirks. For southern users you have to hold down one of the hand controller buttons when turing it on to set it for southern hemisphere. A bit like those watches you buy with the complicated instructions to get it to do something.
It has a high speed switch for slewing and a normal speed for guiding. You have to manually switch over and if you forget and start your autoguiding then the corrections will be massive and you will lose your framing and have to frame the image again. Easy to do at 3am in the morning!
It has a very high quality polar alignment scope. I don't use this as I could not get used to spotting Sigma Octans as it is too dim and hard to distinguish. Some have mastered this and report the polar scope as one of the best out there. I use drift aligning and started using the camera for the drift aligning using Startarg cross hair overlays on the screen to make the process easier.
Some also may not like the threaded counterweight rod but a smooth one is available as an accessory from Robin Cassady. I don't mind as the weights never move which I like.
The clutches are well placed and easy to use.
The mount motors make a pleasing jet like high whine as they wind up to 19,000 to do their job. They are hand wound motors.
FLI filter wheel:
This unit is good but looks a bit shabby against the superior Apogee FW50 filter wheel which is probably the best on the market. It is thin and light but is a bit slow to select a filter. It does achieve good repeatability though.
The washers for holding down the filters are a bit small and there is no provision to handle different thickness filters (it assumes 3mm thick filters - Astronomik filters are 1mm). I give this filter wheel 7 out of 10.
FLI ML8300 camera;
I love this camera. It is an awesome imaging machine. Light, small, no noise, incredible cooling, fast downloads.
It slams the temperature down to -35C when ambient is 22C in about 3 minutes or less - fantastic. It also holds the temperature without overshooting very very accurately more accurate than any other camera (the chip is small though).
No negatives about this camera except that the small well depth (25,000 electrons) means that bright stars bloat more quickly than say an STL11 or an Apogee U16M. But the chip is so defect free and noise free at -35C and very evenly illuminated with no microlense artifacts that you forgive that.
I do notice that stars show the pixels more with this camera but that is probably to do with the sampling and the higher magnification its smaller chip gives. I give this camera 9.5 out of 10 with the .5 deduction for the small well depth of the KAI8300 chip.
Greg.