EQUIPMENT

Astro-Tech AT8RC 8" Ritchey-Chretien

Likes:

• Great bang for the buck!
• True Ritchey-Chretien, with no coma or chromatic aberration.
• Capable of superb images with well-shaped stars across the entire image.
• Plenty of back focus accommodates just about any imaging setup.
• Comes with dual-speed focuser.
  
• Open front eliminates dew problems.
  

Dislikes:

• Field flattener required, as with all Ritchey-Chretiens.
• Flexure in the primary mirror cell necessitates use of OAG.
• Collimation instructions in manual are not good for imaging.
• Focuser is adequate, but somewhat erratic.
  

All Ritchey-Chretiens suffer from field curvature and astigmatism, which results in oblong stars at the edge of the image. This is not coma - the stars are evenly elongated toward and away from the center of the image. Fortunately this problem is magically fixed by using a proven field flattener such as the Astro-Tech ATFF2 or the Astro-Physics CCDT67.

The focuser attaches to the read mirror cell, not the back of the tube, so the weight of the camera causes the position of the primary mirror to flex. Indeed, there are times when flexure can be noticed in exposures as short as 1-2 minutes! Using an off-axis-guider (OAG) solves this and should be considered mandatory for good imaging results.

Improper collimation of the secondary causes stars at one edge to be more oblong than the opposite edge, and improper collimation of the primary results in coma on all stars. Collimation is described on another page.

Now that all the kinks have been worked out, I absolutely love this scope! (Although at one time I was ready to throw it over a cliff.)
 

Orion ED80 APO Refractor

Likes:

• Good, wide-angle performance for the price.
• No coma, like all refractors.
  
• Semi-apochromatic with ED (Extra-low Dispersion) glass results in small amount of chromatic aberration.
• Light enough to double as a guide-scope.
  

Dislikes:

• Not a true apochromatic triplet.

Celestron CI-700 Mount
 
This is a heavy-duty GEM that used to be produced by Celestron to support their C-11 and C-14 SCTs from 1999 to 2003. It's basically a cheaper version of the Losmandy G-11. Although hard to find, some consider it one of the best bargains in the used mount market. In general I'm very happy with this mount, and it serves well for both observing and imaging.

Likes:

• Low Periodic Error (typically 10-15 arc-sec)
• Very Sturdy
• Smooth Drive Corrections (easy to guide)
• Manual Slow-motion Controls
  

Dislikes:

• Slow Slew Speeds
• Polar-finder is small and non-illuminated
• Clutches may slip and bind (can be fixed)
  

 
I've modified the CI700 to improve the action of the clutches, and to allow for quicker and easier set up. See CI700 Mods.


Orion StarShoot Pro V2

Likes:

• Along with the QYH8, perhaps the best bang-for-the-buck for a used CCD one-shot-color camera.
• Real Astro-CCD features: Thermal-electric cooling (TEC) and 16-bit A/D.
• Large pixels results in very good sensitivity.
• IR-cut filter is not aggressive (allows plenty of red).
• Low current draw - 1 amp.
• Proven reliability.

Dislikes:

• Large pixels limit resolution when you zoom-in-and-crop.
• TEC is unregulated and limited to 30 deg C. below ambient.
• Download is slow, about 10 seconds.
  

Someday I'll upgrade to a mono-system with all the neat filters, but for now I have yet to fully utilize this camera to its full potential.


QHYCCD QHY5-IIM Guide Camera:

I was surprised at how easy it is to find guide-stars when this camera is used with an OAG. There was also an immediate improvement in guiding accuracy, probably due to strong
signal/noise ratio that allows more accurate calculation of the star position. Highly recommended!

Likes:

• Very sensitive (QE = 70%), despite being CMOS, 2X2 bin mode = more sensitivity.
• Video, so it can be used for lunar/planetary imaging.
• Small size, light weight.
• Low cost compared to other sensitive guide cameras.

Dislikes:

• Long back-focus of 17mm may present problems when trying to reach focus on an OAG, but nose-piece can be removed.

Orion Deluxe OAG:

Switching from a guide-scope to this OAG completely eliminated the AT8RC flexure problems.

Likes:

• Sturdy, well designed unit.
• 100 degrees rotation without detaching from camera.
• Adjustable tilt pick-off mirror.
• Threaded top of turret rotates for guide camera focus.
  
• Comes with plenty of T-thread spacers and 2" front adapter.

Dislikes:

• Not a "thin" OAG, adds 30mm to back focus requirement.

Past Equipment

Mead 8" SCT OTA
For a few years I used the OTA from a Meade 8" LX50 SCT for long focal-length imaging. The optical quality was good, but not great. There is an expected degree of coma at the edge of the field-of-view, and the corrector lens in front presents dew problems. Over time I finally decided to upgrade to a Ritchey-Chretien.









ADM Side-by-side Platform:
For a few years I mounted the Meade SCT and the ED80 on a side-by-side platform which allowed imaging or guiding through either scope. It's a convenient setup, being able to switch between wide-angle or higher magnification imaging at will. But flexure problems with the new AT8RC forced me to change to an off-axis-guider.

Before that, the ED80 was mounted on the SCT piggy-back style, but sometimes there wasn't enough room to get my head in for finding, framing, or focusing. Switching to a side-by-side platform solved that by allowing plenty of room.

Philips ToUCam Pro 740 Webcam:
Although usable as a guide camera through a guide-scope, it just doesn't have the sensitivity to guide well on anything other than very bright stars. Guiding was sometimes decent, but never great. Don't even think of using it with an OAG. I upgraded to a QHYCCD QHY5-IIM and never looked backed.

Nikon D50 DSLR
The Nikon D50 is a DSLR (digital single lens reflex) camera that uses one of the new generation of full-size format, low-noise high-sensitivity CCD chips. It's similar to the Canon EOS series, except the D50 cannot be controlled by computer software such as Backyard EOS. I had to focus using a par-focal eyepiece, and start/stop exposures using the Nikon remote "clicker". Canons or later model Nikons don't have these problems.

Nikon Infra-red Filter:
All digital cameras have an IR filter because CCD sensors are overly sensitive to red light. The result is that emission nebula lacks that vivid red we love to see, although other objects will image just fine. Removing the IR filter is difficult, but the links page may give you ideas on how to remove it.



Meade 8" LX50 SCT
My 2nd scope was a Meade 8" LX50. Like most SCTs, it offers a good compromise between quality and cost. Using the same fork-arms as the LX200, it may be the sturdiest mount of any mass-produced fork-arm design. It served well for observing and a limited amount of film-based imaging. Later, I mounted the OTA (optical tube assembly) to a Celestron CI700 mount for better and easier guiding.

Jason Schmidt-Newtonian
My 1st scope was an inexpensive one from a department-store, complete with wobbly tripod. But it presented me those first wonderful sights of the rings of Saturn and the Orion Nebula., and propelled my interest in astronomy. I even used it to take photos of the 1991 Solar Eclipse and comet Hale-Bopp. The camera was mounted on the scope piggy-back, and I used the slow-motion knobs to track. (That's right, slowly turning the R/A knob while looking through the eyepiece!)