7" f/12 R35 iStar folded and straight refractor on the Sun.

*

Sunday 1st May and bright sunshine in a cloudless sky as it reached 55F, 13C after an overnight frost. Time to test the new Baader full aperture filter using Astro-Solar foil.

 The Sun's disk with a 640x480  frame size camera setting through 32mm Meade 4000 ep full aperture 180mm Baader Astro-Solar foil filter.

The Sun resized from 3000x3000 on the Ixus 117 compact camera to 1000x1000 in PhotoFiltre. [32mm Meade 4000 S. Plossl ep. This image was taken with the refractor returned to a long straight tube to see if it helped to improve contrast over the folded form. Not visibly thanks goodness! Is that even a good thing? Any slight improvement in sharpness was probably due to the increased altitude of the Sun in the sky by the time I had finished the conversion. There is a very narrow deep violet rim if you enlarge the image by clicking on it. This fringe is completely invisible visually.

The short zoom, compact camera doesn't seem to be behaving as reliably it does on the Moon. There is no sense of a bright uniform disk against a black background in the viewfinder screen. Even the brightness varies across the disk. Giving it almost a pearl-like effect. I keep getting images of dirt and dust instead of the camera focusing on the Sun. This has never occurred before today. I have tried Auto and a whole range of program settings without much success.

There are quite a number of sunspots but they are all rather small. Stopping down the 7" lens to 6" and then 4" aperture seem not to have much effect other than loss of light and easier focusing requirement.

At focus there was no visible limb fringing at any aperture. Though the limb was 'boiling' for most of the morning, in the folded refractor form, it seems to have settled down now. This is despite the roof of the house being below the Sun in the sky from early afternoon. A gentle, easterly wind may be helping to carry the thermal currents away. I have just had to reverse the OTA to the other side of the pier as the sun reached further west. The 7" worm drives on the old mounting seem to be able to cope provided the OTA is well balanced. The OTA balance weight is very helpful to save trying to push the heavy OTA through the loosened rings.

The image shows the straight-tubed 7" f/12 iStar refractor following the sun on the MkIV Fullerscopes mounting on its massive, welded steel pier. The instrument's sheer size is difficult to judge even knowing the main tube is 8" 20cm in diameter and 2m, or over 6 feet long, without the dewshield. The pier flange is 5' [150cm] from the ground without the wheels fitted. The center of the saddle is 2m or 6' 6" above the ground. Even so it it requires a low chair to use the star diagonal as the telescope points higher. I have no great desire to add more mass to the focuser just to lift the telescope higher. So use the trailer jockey wheels when the OTA is in the long, straight tube form.

Lifting the OTA into place ideally requires a short set of builder's steps. Wide rungs are necessary for stability but only three, or possibly four, steps needed in all. The tall folding ladders shown with the telescope are quite stable laterally. But far too steep to provide the stability needed to climb effortlessly to the correct height when carrying a heavy OTA. I have had to rapidly step backwards onto the ground when the ladders have tipped towards me while I was holding the OTA in my arms! These ladders really need several extra pairs of hands to hold on at the same time! They also get in the way during fitting the OTA to the mounting. Only the permanently fitted, short dewshield is in place here. There being absolutely no need for the full dewshield on a warm and sunny day like today.

The telescope was left outside to cool until 10pm when Jupiter was close to the meridian. [South] As the sun had never fallen directly on the tube I imagined it had never really warmed up beyond the 13C, 53F maximum air temperature. The full aperture, solar foil filter should have protected the glass from any heat build up. The OTA certainly felt cool to the touch when I went out to find the temperature had dropped to 42F. Brilliant Jupiter had reached about 42 degrees local altitude. Unfortunately there was little to be seen beyond two dark belts and a hint of a third. No power I tried up to and over 250x made the planet any clearer. As usual, I tried the Yellow No8 and then the Fringe Killer filters but they made no visible difference to clarity. There was no finer detail, at all, to be seen.

Click on any image for an enlargement.

*