02/09/06

On the 26th August 2005 my AP 160mm EDF F7.5 (FL 1200mm) arrived having first put my name on the AP 155 waiting list in July 1999. This is my fourth AP product having bought an AP130EDT in 1995, AP1200 in 1999 and an AP400 in 2001, I sold the 5 inch 3 years ago in anticipation of the AP155 but I failed to make the cut a couple of years ago! Since I ordered the scope, AP redesigned the 6 inch refractor and now constitutes a 6.3 inch air spaced triplet with a 4 inch focuser as standard and I upgraded to the feathertouch option.

The AP160EDF is beautiful to look at with gorgeous machining, the new 4 inch focuser is very solid and smooth. I like the addition of the rotating focuser which is very useful for CCD imaging. I did notice that when tightening the locking ring, the focuser needs to be held to prevent rotating too. Also the upgraded feather touch focuser is very accurate and free of backlash, but when the locked sufficiently to prevent the draw tube from moving with a CCD camera attached, the fine focuser knob is quite tight and springs back a little when moving against gravity. The 4 inch focuser extension is now held in place with locking screws rather than threaded attachments, therefore much easier and quicker to remove especially when cold! The weight of the OTA is 27lb and easily manageable by one person. Included is a rugged case shown in the photo below.

 I have now managed 3 nights with this scope and very pleased so far. My first night was dedicated to visual use which didn't disappoint. Initially a star test showed a perfect in and outside patterns except the outer ring which was brighter outside focus, however a repeat test another night (much later in the night) showed virtually identical patterns, so I assume a cool down effect? (see image below for the latter star test with a CCD camera, I defocused about 1/4 turn of the coarse knob). An in focus star test revealed a tight airy disk with a very faint first diffraction ring - a good sign that nearly all the light is concentrated in the airy disk. What struck me immediately was the high contrast with dark background of deep sky objects, I haven't witnessed this before in any other scope. I had wonderful views of the Veil, M27, M15, double cluster (this was exquisite in this size scope with a 31mm Nagler) and a few double stars including of course, the double double in Lyra).

The next two nights involved CCD imaging. Firstly I tried my STL11k (images not shown) and found that a field flattener is required due to comatic shaped stars in the corners (field curvature), but not as severe as I expected for this large 35mm chip. Marj told me the field flattener-corrector will be available shortly. I then concentrated on the ST10 and the stars with this chip were excellent right to the corners and I took an image of the Pac man nebula. Again I noticed how low the background count was with no correction due to light pollution gradients required.

So thanks to Roland and Marj (and the rest of the AP crew) for this great new addition to their portfolio, it will give me great pleasure over the years to come!