1st ASK3 Image from S'pore (New image added From Good Fri)

[Valery]

Thanks Alexandra. Lots of work needed to bring out its best performance.

This is not true, Alfred. What you really did with ARIES components? I believe you did nothing with them.

All problems were as you have finally realized in a LS50THa which were not up to necessary level.
Finally you found a good sample which has a good performance.

The second your problem was that you have the difficulty to attach a camera and a barlow lens to the LS50THa telescope.

And these difficulties can be described as needed a lot of work. If only your LS50THa will be OK from the first time and
if you have right camera and barlow you'd nothing to do to make it work - it will work right out of the box, plug and play.


Valery

[yltansg]

Thanks Mark for your kind comments.

Valery is right, I did not have to do any work on ASK 3 components. Valery provided simple instructions and ASK 3 was easy to assemble.

All the work was done on getting the right equipment and getting them to work well. On top of my Lunt LS50THA, I had to borrow 2 more LS50THA to find the one that is good. Have to thank my friends for lending their equipment and Valery for pointing out what to look for, etc. Before this, I had to source for 2 small signature adapters to use with the BF1200 to achieve focus with cameras. I tried 3 different types of barlows without success and tried to buy the barlows that Valery used. I wrote to WO and NPZ to buy barlows but without success. Then I tried 4 different types of cameras before settling on PG Grasshopper 3. Many of these work are necessary because I am using ASK 3 for the first time. I believe that it will get better as I get more familiar with the equipment.

Right now I am still getting uneven image and inconsistent contrast. This is the first time I am using a LS50THA and I believe getting good contrast and even image will come by with more practice, hopefully it is not an equipment problem. Every bit of work is worth it because I am improving

Here is one more image from yesterday. This time I used another camera - Grasshopper 50S5M.
This is a cropped image to remove the parts that have uneven contrast.

I am still not quite happy with it because I believe the contrast and focus can be better. I also have a long way to improve my post processing workflow.

By the way, my ASK is Version 3, an improvement over the previous version. I am glad to get V3 because I thought I was getting V2 or V2.5 when I made a commitment to buy.

Thanks Valery for a fine piece of optics and the good instructions certainly help.

Alfred

[eroel]

Alfred:
Super instrument and mod. The result are super images.
Well done,
Eric.

[Derek Klepp]

Nearly missed these thanks Alfred.

[yltansg]

Hi Eric and Derek,

Thanks for your kind comments. There are still many areas of improvement to work on, especially on my skills.

Alfred

[Valery]

Alfred,

The unevenness is the immanent sign of a small sub aperture etalon. The larger the ratio
Dobj / Det the smaller sweet spot will be seen.

The best is an objective (front mounted) etalon. If the etalonis smaller than objective and it is
internally mounted (with increased field angle) then a sweet spot will starts to shrink.

In the ideally made telescope with etalon size equal to 1/2 of an feeding aperture size and about 0,7A
bandwide, the sweet spot will be of 1/2 degree in diameter = about the sun diameter.
In such a telescope we can see a full sun disk in H-a with maximal contrast at the center and somewhat
lesser contrast at the limb where the bandpass of the etalon shifts towards blue (starts to leave the H-a
from the blue wing) and transmit less H-a and more continuum light.

Your etalon size is 1/7,5 of the feeding aperture size. So, it the case of 0,7A bandpass the sweet spot
diameter will be about 1/4 of the sun disk. Judging the H-a structures on your pictures I can estimate
your LS50THa etalon as about 0,5A or even slightly narrower (which is very nice ended). Therefore
the sweet spot in this your setup is even smaller than 1/4 sun disk circle. May be 1/5 or less.

What you can adjust is make it maximally symmetrical in the FOV.

Then you can work in such ways:

1. Use a barlow lens in a front of your blocking filter. This will increase liner size of the sweet spot and
can fully cover your camera chip (if the chip use is not too large).
In this case (slower F/D at the entrance of the BF) the blocking filter will work even better and better blocks
continuum light. The drawback is exposure time increasing.

2. Use smaller chip

3. Use a ROI with rectangle inscribed in a sweet spot circle.

No other optimizing is possible in this system. The small size of the sweet spot is its principal limitation and
this is the payment for it's lower cost.


IMPORTANT: the ASK-3 consists also all the components of the ASK-1 and ASK-2. So, you can use your
150mm telescope in a several combinations:

1. ASK-1 when a LS50FHa used as an etalon + refocusing objective + focuser + BF + camera.
If a LS50FHa is good and not require the tilt to get in a CWL of H-a, then you will have full disk in H-a
like you have it in a LS50THa itself.

2. ASK-2 - you can use two LS50FHa and have a DS.

3. You can place a good LS50FHa between the first component of the ASK and your present LS50THa and get
a DS system.


I believe that with a time and more experience you will give this kit a full use in different combinations.

Good luck.

Valery

[yltansg]

Valery,

With your explanation, I now understand what I have experienced. I will try to put a barlow in front of the blocking filter this weekend and also the double-stacked configuration. Thanks for your help.

I didn't realise the ASK3 is so versatile. Great job on the design.

Alfred

[yltansg]

Here is another image from my first light of this hybrid scope on Good Friday. Are those bubbles?

[marktownley]

Nice addition Alfred!