DIY Equatorial Wedge

[Chanlunlun]

The equatorial wedge for cpc1100 is very expensive ( HKD 3500 +) and even though you are willing to pay, you just have no idea when you will receive it. Most probably you won't make it before April, when the hot shooting session of 4 planets approaches.

So I have decided to DIY one. It's just a barn door design and cost no more than a hundred dollar, 35 times cheaper than the original one and, more importantly, no waiting time. I only spend one day to complete the job.

Is it sturdily solid ? No.
Does it work ? Yes.

[bbyaya]

Good Job

[Chanlunlun]

Good Job

Thanks.

My job is far from good. My craftsmenship is notoriously poor. Anyway it's still an equatorial wedge and the alt-azm telesocpe can be changed into equatorial action.

Planetary shooting will be done in a more conveniet way.

[Skyobs]

Why an equatorial mount is more convenient for planetary shooting? I guess field rotation is not a concern for such short exposure, and tracking is also not a concern with CPC? Is vibration in DEC motion still a significant problem at high power?

[Subaru]

I guess field rotation is most severe around Zenith, so equatorial mount is always preferred unless a field derotator is deployed.

[鄧登凳]

Dear god of mirrors,

Would you consider adding a polar scope (or even a red dot finder) there to help polar alignment?

Regards,
Tang

[Chanlunlun]

Why an equatorial mount is more convenient for planetary shooting? I guess field rotation is not a concern for such short exposure, and tracking is also not a concern with CPC? Is vibration in DEC motion still a significant problem at high power?

Field rotation is a major concern.

In zenith the field will rotate nearly 10 degrees during , say, 3 minutes of shooting period. Zenith is the best shooting place for high power planetary. It means that alt-azm mount must surrender the best shooting spot in the sky.

Even in very modest position in the sky field rotation can easily reach 1 degree per 5 minutes shooting. For C-11 to obtain best result blurring due to field rotation could not exceed 0.3 arsec ( i.e. about 2 to 3 pixels in the CCD chip ) which means than in most part of the sky alt-azm mount cannot be employed unless your shooting period is short enough. Too short shooting period cannot capture enough frames for processing.

Hence for best result in planetary shooting an equatorial mount is a must. So I DIY the wedge since a Celestron wedge is not available in market. (No way to contact BossKwan!!)

[Chanlunlun]

Dear god of mirrors,

Would you consider adding a polar scope (or even a red dot finder) there to help polar alignment?

Regards,
Tang

The polar alignmemt will be carried out by drifting method.

[鄧登凳]

The polar alignmemt will be carried out by drifting method.

Would drift alignment be difficult without an azimuth adjustment mechanism?

BTW, if field rotation for planetary imaging is your concern, Registax can de-rotate by multipoint alignment. If you are not statisfied with that derotation process, here is a VBScript programming to deal with it: http://www.leif.org/mikael/derotation.html

[bingsze]

Dear god of mirrors,

Would you consider adding a polar scope (or even a red dot finder) there to help polar alignment?

Regards,
Tang

The polar alignmemt will be carried out by drifting method.

如果用漂移大法，有沒有微調可以較。

[Chanlunlun]

Would drift alignment be difficult without an azimuth adjustment mechanism?

Rather difficult but not impossible.

BTW, if field rotation for planetary imaging is your concern, Registax can de-rotate by multipoint alignment.

Multipoint alignment does not work well with high power planetary sequence. It manage to de-rotate the image while at the same time lower the image quality.

If you are not statisfied with that derotation process, here is a VBScript programming to deal with it: http://www.leif.org/mikael/derotation.html

The VBScript seems to be too far away from my knowledge. I have no idea how to play around with them.

[Skyobs]

Multipoint alignment does not work well with high power planetary sequence. It manage to de-rotate the image while at the same time lower the image quality.

I see. Thanks (and also to Subaru).