M42 dari KL bandar.

[mymoon]

Jam 12 mlm tompok awan dah mula. Bulan dan Musytari dah di lindunginya..

Orion di timur dah 45 darjah dan clear.

bebelah bagi nak bawa keluar align Equatorial mount atau guna Mni Tower Alt Az mount.

Canon 60D dan 200mm f/2.8 masih di Mini Tower. Entah berapa lama masa tinggal sebelum langit ditutup awan.

Cuba lah wide angle Deepsky photo. Slew Mini Tower ke Orion Nebula.

BackYardEOS ada focussing tool. Manual focus dengan guna bintang di Orion.

Check exposure histogram. Dari tempat imaging dengan lens  f/2.8 max exposure ialah 9sec at ISO 3200.

Jadi kalau guna telescope f5.6 max 36sec at ISO 3200. Bintang dah memajang.

Set exposure, jumlah shots, ISO, tekan start.

Hasilnya




Tak cukup light frames. Mungkin kena 70X 9sec kot lebih kurang 10 min tiap2 satu.


cheers

[shahgazer]

ASW.

Interesting experiment. How do you find BYE? adakah ia banyak membantu?

[mymoon]

Interesting indeed.

Just to confuse the beginners. Aperture for visual and astrophotography has different meaning

Coming from visual astronomy the word Aperture means diameter (usually in inches)  of front of telescope. Rarely variable mostly fixed.
click here

Coming from land based photography Aperture means how wide is the opening of the diaphgram inside a lense. Very rarely fixed, mostly  variable.
commonly reffered to as f stop. click   here

To Astronomers it is the focal ratio is what to photographers is the f stop. Please correct me if  I am wrong.

Depending on the background of the lecturer there may be some confusion.
So take care when attending astrophotography talks or classes.

So for astrophotography the wider the f stop (the smaller the number, sorry chaps) ie the faster  the lense/telescope the shorter will be the time taken to shoot. The shorter the time means  less dependent on mounts.

The usual story is for astrophotography you will need an equatorial mount. This started from the early days of visual telescope of focal ratio of  12.


In the example of M42, I use a focal length of 200mm  f/2.8 lense expose for 9 sec. Hardly any bloated star on  a Alt Az mount.

Assuming there is such a telescope of a focal length of 200mm and a focal ratio of 12 ( Aperture is only 200/12 about 16.7mm)  the equivalent exposure time required is 144sec(9X2^4). Using an Alt Az mount you will definately get star trails.

So the wider the lense/telescope (now we are talking astrophotography) the shorter is the time for exposure, the less demand on the mount.

Unfortunately a 200mm f/2.8 cost only around RM2,000 but a 200mm f/2.0 cost RM20,000 or ten times.

and a 50mm f/1.8 cost around RM300, a 50mm f/1.4 cost RM1500 whilst a 50mm f1.2 cost RM 5000.


So for astrophotography use buy the fastest telescope/lense you can afford for the required focal length.

Planets - Long focal length. For Deep Space Objects (DSO) you generally need a short focal length.


For visual use the Aperture fever applies.



BTW I have tried to bring out the Running man nebula from my second attempt at processing  M42.



with proper planning the horse head and flame nebula could have been included.

Any corrections or comments most welcome. Hey I am new too to astronomy. 

Pray for clear skies so that my 560mm f/2 can get its first light. 

cheers

[redzuan]

Pray for clear skies so that my 560mm f/2 can get its first light. 

cheers

It is finally here... 

Now for the starlight express or QHY8...

Or more clouds and thunderstorms for the next few months... (curse of new astro equipments)

p/s: the long introduction was surely to offset the mind off from the grand  finale ending!

[haldafluke]

It is finally here... 

Now for the starlight express or QHY8...

Or more clouds and thunderstorms for the next few months... (curse of new astro equipments)

p/s: the long introduction was surely to offset the mind off from the grand  finale ending!

Now we have got someone to point to if the clouds starts rolling every night.

[aus]

cantiknya, sepatutnya leh nampak horsehead dgn 200mm f2.8 ni??? sy ada merujuk web yg agak lama ni,hasilnya jgk agak puas hati.. http://www.ssoastro.org/lenses_for_piggyback_astrophotog.htm, imejnya sgt detail walaupun dgn lens yg murah..maaf jika sy mencelah dgn abg2 pro kat cni hehe 

[mymoon]

cantiknya, sepatutnya leh nampak horsehead dgn 200mm f2.8 ni??? sy ada merujuk web yg agak lama ni,hasilnya jgk agak puas hati.. http://www.ssoastro.org/lenses_for_piggyback_astrophotog.htm, imejnya sgt detail walaupun dgn lens yg murah..maaf jika sy mencelah dgn abg2 pro kat cni hehe 

betul tu tak payah beli lense yang mahal dan yang baru. apa lense pun boleh guna. cuma kalau guna pentax, soligor, M42 Carl Zeiss Jena Manual focus lens,  kena beli adapter untuk canon.

sila klik disini terhad untuk lense yang sudah di cuba beliau.

apa yang saya maksudkan tentang termasuk horsehead dan flame nebula jikalau cermat framing.

Maaf contoh tak sama dengan aspect ratio gambar yang diambil



apa yang patut di frame semasa composition  ialah



Tiap2 lense ada Field of View(FOV) tersendiri  . Ianya bergantung kepada focal length

effective  FOV bergantung  kepada kamera yang diguna samada full frame(X1), 1.3 APC , 1.6 atau 1.5 .

dengan pertolongan klik ini untuk kamera Canon 60d dan lense 200mm effective FOV ialah 6.4X4.3

guna stellarium software untuk effective FOV saperti yang di nyatakan.

 frame dalam LCD/eyepiece saperti contoh diatas sebelum tekan shutter.

BTW piggy back bermakna kamera dengan lense diatas telescope Alt Az mount dengan wegde sama saperti Equatorial mount. Legacy lah. Ini Saudara Shah boleh cerita panjang.

cheers